Short answer
The Islam of the Qur'an and the Sunnah, the same Islam as the Prophet's (ﷺ) companions. Ali's own reports show this. He showed how the Prophet (ﷺ) made wudu, and he washed his feet. He gave the time limit for wiping over leather socks. He reported that the Prophet (ﷺ) forbade temporary marriage. He named Abu Bakr and Umar the best after the Prophet (ﷺ), and as caliph he kept the earlier judgments. The prayers he passed on in the sound reports call on Allah (﷾) alone. In the prayer the Prophet (ﷺ) is blessed, as Allah (﷾) commanded, and his family, Ali among them, is blessed with him in the words he taught. We love Ali, and love for Ali means doing as Ali did.
Full explanation
Ali held to the Book and the Sunnah
Ali's own words show where he stood. He was asked whether his family had any book besides the Qur'an. He said no, only the Book of Allah (﷾), the understanding Allah (﷾) gives a Muslim, and what was written on one sheet: rules on blood-money, freeing captives and retaliation. Allah's (﷾) rule for every Muslim is the same: obey Allah (﷾) and the Messenger, and if you differ, refer it to Allah (﷾) and His Messenger. Ali followed that rule, and so do we.
Abu Juhayfa asked Ali whether the family had any book besides the Qur'an. Ali said no: only the Book of Allah, the understanding Allah gives a Muslim, and what is on this sheet. The sheet held rules on blood-money, on ransoming captives, and a ruling on retaliation (qisas).
“O ye who believe! Obey Allah, and obey the Messenger, and those charged with authority among you. If ye differ in anything among yourselves, refer it to Allah and His Messenger, if ye do believe in Allah and the Last Day: That is best, and most suitable for final determination.”
How Ali washed for prayer
The Qur'an lists the face, the arms to the elbows, the head, and the feet to the ankles. Ali showed how the Prophet (ﷺ) did it. Those who saw Ali's wudu, or asked him about it, report that he washed his face and arms three times, wiped his head, then washed his feet. He said he wanted to show them how the Messenger of Allah (ﷺ) made wudu. In one report, Ali then stood and drank the water that was left.
“O ye who believe! when ye prepare for prayer, wash your faces, and your hands (and arms) to the elbows; Rub your heads (with water); and (wash) your feet to the ankles. If ye are in a state of ceremonial impurity, bathe your whole body. But if ye are ill, or on a journey, or one of you cometh from offices of nature, or ye have been in contact with women, and ye find no water, then take for yourselves clean sand or earth, and rub therewith your faces and hands, Allah doth not wish to place you in a difficulty, but to make you clean, and to complete his favour to you, that ye may be grateful.”
Zirr ibn Hubaysh reports that Ali was asked how the Messenger of Allah (ﷺ) performed wudu. Ali described it, wiped his head, then washed his feet three times, and said: this is how the Messenger of Allah (ﷺ) performed wudu.
Abu Hayya saw Ali perform wudu, washing each part three times, wiping his head, then washing his feet to the ankles. Ali said he wanted to show how the Messenger of Allah (ﷺ) performed wudu.
Abu Hayya saw Ali perform wudu. He washed his hands, rinsed his mouth and nose three times, washed his face and forearms three times, wiped his head once, and washed his feet to the ankles. He then drank the water left over, standing, and said he wanted to show how the Messenger of Allah (ﷺ) purified himself.
Wiping over leather socks
Wiping over leather socks, when they are worn, is also part of the Prophet's (ﷺ) practice. Shurayh went to Aisha to ask about it. She sent him to Ali, because Ali used to travel with the Messenger of Allah (ﷺ). Ali gave the answer. The Prophet (ﷺ) set three days and three nights for a traveller, and one day and one night for a resident. The mother of the believers trusted Ali's knowledge of the Sunnah, and so do we.
Shurayh ibn Hani went to Aisha to ask about wiping over leather socks. She told him to ask Ali, the son of Abu Talib, because he used to travel with the Messenger of Allah (ﷺ). They asked Ali, and he said the Messenger of Allah (ﷺ) set a limit of three days and three nights for a traveller and one day and one night for a resident.
What Ali reported about temporary marriage
Ali reported that on the day of Khaybar the Messenger of Allah (ﷺ) forbade temporary marriage and the eating of domestic donkey meat. He told this to Ibn Abbas himself. Another companion, Sabra, was with the Prophet (ﷺ) at the Conquest of Mecca, where the permission was given for a short time. He reports that the Prophet (ﷺ) then said Allah (﷾) had forbidden it until the Day of Resurrection. So it is Ali's own report that the Prophet (ﷺ) ended it. Scholars explain it was allowed for a time on campaigns, then forbidden for good.
Ali ibn Abi Talib reports that on the day of Khaybar the Messenger of Allah (ﷺ) forbade temporary marriage and the eating of the meat of domestic donkeys.
Ali tells Ibn Abbas that at the time of Khaybar the Prophet (ﷺ) forbade temporary marriage (mut'a) and the eating of donkey meat.
Ali ibn Abi Talib reports that the Messenger of Allah (ﷺ) forbade, on the day of Khaybar, temporary marriage with women and the eating of the flesh of domestic donkeys.
Sabra al-Juhani reports that the Messenger of Allah (ﷺ) said: people, I had permitted you temporary marriage with women, but Allah has now forbidden it until the Day of Resurrection. Whoever has such a wife should let her go, and take back nothing he gave her.
Sabra al-Juhani's son reports that his father went with the Messenger of Allah (ﷺ) on the expedition of the Conquest of Mecca, and that during their stay the Prophet (ﷺ) permitted temporary marriage.
How Ali prayed and called on his Lord
Ali narrated how the Prophet (ﷺ) prayed. When he stood to pray, the Prophet (ﷺ) turned his face to the One who originated the heavens and the earth. He said that his prayer, sacrifice, life and death are for Allah (﷾). He asked Allah (﷾) alone for forgiveness and guidance. Ali also reports that the Prophet (ﷺ) forbade him to recite the Qur'an in bowing and prostration. This is the prayer Ali passed on.
Ali ibn Abi Talib reports how the Prophet (ﷺ) opened his prayer and what he said in it when he stood to pray. He began by turning his face to the One who originated the heavens and the earth, saying that his prayer, sacrifice, living and dying are for Allah, Lord of the worlds, who has no partner. He asked Allah alone for forgiveness and guidance. In bowing, rising and prostrating he addressed Allah alone, and between the tashahhud and the salutation he asked Allah to forgive his earlier and later sins.
Ali ibn Abi Talib reports that the Messenger of Allah (ﷺ) forbade him to recite the Qur'an while bowing or prostrating.
“Say: "Truly, my prayer and my service of sacrifice, my life and my death, are (all) for Allah, the Cherisher of the Worlds: No partner hath He: this am I commanded, and I am the first of those who bow to His will.”
Ali called on Allah (﷾) alone
The prayers Ali passed on in the sound reports call on Allah (﷾) alone. The Prophet (ﷺ) taught Ali to say: O Allah (﷾), guide me and keep me straight. He taught Ali and Fatima to say Allahu akbar, SubhanAllah and Alhamdulillah when they lay down. Another supplication Ali narrated opens the prayer by turning the face to the One who originated the heavens and the earth. No sound report has Ali putting himself into the prayer. The testimony of faith names only Allah (﷾) and His Messenger. The tashahhud (the words said while sitting in prayer) gives all praise to Allah (﷾), greets the Prophet (ﷺ) and every righteous servant of Allah (﷾), asks nothing of any of them, and ends with the same testimony. When companions greeted people by name in it, the Prophet (ﷺ) gave them one greeting that reaches every righteous servant instead.
Ali reports that the Messenger of Allah (ﷺ) told him to say: O Allah, guide me and keep me straight. He was to keep in mind the right path and the straightness of an arrow.
Ali reports that Fatima asked for a servant because the hand mill hurt her. The Prophet (ﷺ) came to their bed and said he would teach them something better than a servant. When they went to bed they should say Allahu akbar thirty-four times, SubhanAllah thirty-three times and Alhamdulillah thirty-three times.
Ali ibn Abi Talib reports how the Prophet (ﷺ) opened his prayer and what he said in it when he stood to pray. He began by turning his face to the One who originated the heavens and the earth, saying that his prayer, sacrifice, living and dying are for Allah, Lord of the worlds, who has no partner. He asked Allah alone for forgiveness and guidance. In bowing, rising and prostrating he addressed Allah alone, and between the tashahhud and the salutation he asked Allah to forgive his earlier and later sins.
Umar ibn al-Khattab reports that a stranger in very white clothes, with no sign of travel on him, sat before the Prophet (ﷺ) and asked him about Islam, faith and excellence in worship. Asked about faith, the Prophet said it is to believe in Allah, His angels, His books, His messengers and the Last Day, and to believe in the divine decree, its good and its evil. Afterwards the Prophet told Umar the stranger was Gabriel, who had come to teach them their religion.
Ibn Umar reports that the Prophet (ﷺ) said Islam is built on five: to bear witness that there is no god but Allah and that Muhammad is the Messenger of Allah, to establish the prayer, to pay zakah, to perform the pilgrimage, and to fast the month of Ramadan.
Abdullah ibn Mas'ud reports that behind the Prophet (ﷺ) the companions used to say in the sitting: peace on Jibril, peace on Mika'il, peace on so-and-so. The Messenger of Allah (ﷺ) turned and said that Allah Himself is As-Salam, and taught them to say: all compliments, prayers and good things are due to Allah; peace on you, O Prophet, and Allah's mercy and blessings; peace on us and on the righteous servants of Allah. He said this greeting reaches every righteous servant in heaven and earth. Then: I testify that there is no god but Allah, and I testify that Muhammad is His servant and Messenger.
Who is named in the prayer
Allah (﷾) commands blessings on the Prophet (ﷺ), and the tashahhud (the words said while sitting in prayer) bears witness that Muhammad is His servant and messenger. So the Prophet (ﷺ) is named in the testimony and the prayer because Allah (﷾) made it part of the faith. His family is honoured too. The companions asked how to ask Allah (﷾) to bless him and his family. He taught them to say: O Allah (﷾), send blessings on Muhammad (ﷺ) and on his family. Ali is among that family, and he prayed with these words. No sound report has the Prophet (ﷺ) or Ali adding a testimony about Ali to the prayer, the call to prayer or the testimony of faith.
“Allah and His angels send blessings on the Prophet: O ye that believe! Send ye blessings on him, and salute him with all respect.”
Abdullah ibn Mas'ud reports that behind the Prophet (ﷺ) the companions used to say in the sitting: peace on Jibril, peace on Mika'il, peace on so-and-so. The Messenger of Allah (ﷺ) turned and said that Allah Himself is As-Salam, and taught them to say: all compliments, prayers and good things are due to Allah; peace on you, O Prophet, and Allah's mercy and blessings; peace on us and on the righteous servants of Allah. He said this greeting reaches every righteous servant in heaven and earth. Then: I testify that there is no god but Allah, and I testify that Muhammad is His servant and Messenger.
Ka'b ibn Ujra reports that the companions asked the Messenger of Allah (ﷺ) how to ask Allah to send blessings on him and on the members of his family, since Allah had taught them how to greet him in the prayer. He told them to say: O Allah, send mercy on Muhammad (ﷺ) and on the family of Muhammad, as You sent it on Ibrahim and on the family of Ibrahim, for You are Most Praiseworthy, Most Glorious. O Allah, bless Muhammad and the family of Muhammad, as You blessed Ibrahim and the family of Ibrahim.
Zayd ibn Arqam reports that at a watering place called Khumm, between Mecca and Medina, the Prophet (ﷺ) praised Allah and said he was leaving two weighty things among the people: the Book of Allah, which holds right guidance and light, so hold fast to it; and the people of his household, reminding the people of their duties to the members of his family. Zayd said the Prophet's (ﷺ) wives are of his household, but the household meant here are those to whom charity is forbidden: the family of Ali, of Aqil, of Ja'far and of al-Abbas.
Ali and Abu Bakr and Umar
Ali named Abu Bakr first and then Umar as the best of people after the Prophet (ﷺ). He gave his pledge to Abu Bakr, praising his right. He gave the pledge to Uthman when the six men named by Umar met to choose his successor, and he asked Allah's (﷾) mercy for Umar when his body was laid out. Ali's daughter Umm Kulthum was Umar's wife. Ali walked with these men and honoured them.
Ali's son Ibn al-Hanafiyya asked his father who the best of people were after the Messenger of Allah (ﷺ). Ali answered Abu Bakr, then Umar. Afraid that Ali would name Uthman next, he asked: then you? Ali replied that he was only a man among the Muslims.
In a long report from Aisha, Ali, who had not given his pledge during the six months of Fatima's life after the Prophet's (ﷺ) death, seeks reconciliation with Abu Bakr once she has died. He sends for Abu Bakr, and Abu Bakr comes to him. Ali says the family know Abu Bakr's excellence and what Allah has given him, and do not envy it, but that Abu Bakr had not consulted them, and they had thought they had a right in the matter because of their kinship to the Messenger (ﷺ). Abu Bakr weeps and says that kindness to the relatives of the Messenger (ﷺ) is dearer to him than kindness to his own. Ali gives him his pledge of allegiance that afternoon and praises Abu Bakr's right in public. The Muslims are glad and draw close to Ali again. The same report begins with Fatima's request about her inheritance; that part is discussed on the page "Was Fatima angry with Abu Bakr?".
In the long report of Umar's death, Umar names six men to choose among themselves. The choice comes down to Uthman and Ali, and Abd al-Rahman ibn Awf asks each in turn to promise that he will do justice if chosen, and listen and obey the other if the other is chosen. Both agree. Abd al-Rahman pledges to Uthman, and Ali gives him the pledge of allegiance, then all the people of Medina do.
Ibn Abbas reports that when Umar's body was laid out and the people prayed for him, Ali came, asked Allah's mercy for Umar and said that no one's deeds were dearer to him to meet Allah with than Umar's. Ali said he had always thought Allah would place Umar with his two companions, because he often heard the Prophet (ﷺ) say: I, Abu Bakr and Umar went; I, Abu Bakr and Umar entered.
Umar divided garments among the women of Medina, and one good garment was left. A man told him to give it to his wife, the granddaughter of the Messenger of Allah (ﷺ), meaning Umm Kulthum, the daughter of Ali. Umar gave it to Umm Salit instead, a woman of the Ansar who had carried water-skins for the Muslims at Uhud.
As caliph, Ali kept what had been done
When Ali ruled, he told the people of Iraq to judge as they used to judge, because he disliked disagreement. He kept the earlier judgments for the sake of unity. Ali brought nothing new into the religion. He held to what the Prophet (ﷺ) left.
Ubayda reports that Ali told the people of Iraq to judge as they used to judge, because he disliked disagreement, until the people united as one group or he died as his companions had died.
Loving Ali means doing as Ali did
Ali is loved by Allah (﷾) and His Messenger. The Prophet (ﷺ) said he would give the flag to a man who loves Allah (﷾) and His Messenger, and that man was Ali. Ali swore the Prophet (ﷺ) had promised him that only a believer would love him. The best way to honour him is to follow what he followed: the Qur'an and the Sunnah of the Messenger of Allah (ﷺ).
Salama reports that Ali had stayed behind at the time of Khaybar because of eye trouble, then set out after the Prophet (ﷺ). On the eve of the conquest of Khaybar the Prophet said that the next day he would give the flag to a man who loves Allah and His Messenger, and that Allah would grant victory under his leadership. Ali arrived unexpectedly, the Prophet gave him the flag, and Allah granted victory under his leadership.
Ali swore by the One who splits the seed and creates life that the Prophet (ﷺ) had promised him that only a believer would love him, and only a hypocrite would hate him.
“Say: "If ye do love Allah, Follow me: Allah will love you and forgive you your sins: For Allah is Oft-Forgiving, Most Merciful."”
Perspectives
Some Muslims believe Ali practised differently from the companions
Some Muslims, out of love for Ali, hold that his practice was different from what the other companions did. They bring these arguments.
Temporary marriage was not forbidden by the Prophet (ﷺ); it was stopped later.
Rebuttal
Ali himself reports that the Prophet (ﷺ) forbade it, and said so to Ibn Abbas, who held another view. Sabra reports the Prophet's (ﷺ) own words that Allah (﷾) has forbidden it until the Day of Resurrection. Scholars explain it was allowed for a time on campaigns, then forbidden for good.
Ali wiped his feet in wudu, because the Qur'an says to wipe the head and the feet.
Rebuttal
In the reading most widely recited, the feet are joined to the parts that are washed. They are given a limit, "to the ankles", as the arms are given "to the elbows". The verse is recited in two ways, so the Prophet's (ﷺ) practice settles it. Ali showed that practice: he washed his feet. The Prophet (ﷺ) also called out to companions who were only passing wet hands over their feet. He told them to save their heels from the Fire. In one report Ali only passed wet hands over his feet. He said this was the wudu of someone whose wudu was still intact: a renewal, not the wudu the verse requires.
Ali's pledge to those before him was late and unwilling.
Rebuttal
Ali gave his pledge to Abu Bakr, saying the family did not envy what Allah (﷾) had given him. He praised his right in public. He gave his pledge to Uthman. He named Abu Bakr and Umar the best after the Prophet (ﷺ). He said no one's deeds were dearer to him to meet Allah (﷾) with than Umar's. And he told the people of Iraq to keep judging as before.
A testimony to Ali belongs in the faith, because the Prophet (ﷺ) declared Ali's place himself.
Rebuttal
We love Ali. But the words of the testimony and the prayer were not left to anyone's choice. Allah (﷾) told the Prophet (ﷺ) to declare his message: "I am sent unto you all, as the Messenger of Allah". When he listed what Islam is built on, he named two testimonies, to Allah (﷾) and to His Messenger, and nothing more. At Khumm, in the sound report, he asked the people to hold fast to the Book of Allah (﷾) and reminded them of their duties to his family; he added no testimony. No sound report has Ali, who passed on so much of the prayer, teaching one either.
Calling on Ali is only asking him to pray to Allah for us.
Rebuttal
Asking a living person to pray for you is right. But calling on someone absent for what only Allah (﷾) gives is what the Qur'an forbids, and the supplications Ali passed on in the sound reports call on Allah (﷾) directly. The page "Can a Muslim call on anyone but Allah for help?" gives the evidence.
The Islamic perspective
Ali practised the Islam of the Qur'an and the Sunnah, as the companions did. His own reports show it: how he washed, how he prayed, what he forbade, whom he honoured, and what he kept. Love for Ali means doing as Ali did.
Ali washed his feet in wudu and reported that this is how the Messenger of Allah (ﷺ) made wudu.
Ali gave the Prophet's (ﷺ) time limits for wiping over leather socks, and Aisha sent people to him for it.
Ali reported that the Prophet (ﷺ) forbade temporary marriage.
The prayers Ali passed on in the sound reports call on Allah (﷾) alone.
Ali named Abu Bakr and Umar the best after the Prophet (ﷺ), and pledged to those before him.
The Prophet (ﷺ) is blessed in the prayer, as Allah (﷾) commanded. His family, Ali among them, is blessed with him in the words he taught.
As caliph, Ali told the people of Iraq to judge as they used to judge.
Following Ali means following what Ali followed, the Qur'an and the Sunnah.