Short answer
Most scholars today say it is. Islam teaches that your life and health are a trust from God (﷾), not yours to wear away. The Qur'an says: "make not your own hands contribute to (your) destruction". It also says: "Nor kill (or destroy) yourselves". Tobacco reached Muslim lands only around 1600, so no verse or hadith names it, and when it was new, scholars differed, because its harm was not yet known. Now it is. The World Health Organization says tobacco kills more than 7 million people a year, over 1.6 million of them non-smokers who breathe in others' smoke, and that there is no safe level. So most scholars now hold that smoking is forbidden, and the same reasoning covers the water pipe (shisha). Islam's way with a smoker is mercy. Anyone who wants to stop should be helped, not shamed, and no one has to quit before becoming a Muslim.
Full explanation
Why no verse names it
Tobacco comes from the Americas. It reached Muslim lands at the end of the tenth and the start of the eleventh Islamic century, around 1600. So the Qur'an and the hadith do not name it, any more than they name heroin. The scholars judged it by the principles of the Sharia, and the main principle is harm. Where the harm the Sharia forbids is established, a thing is forbidden. Where it is not, it may be disliked or allowed. That is why scholars differed about tobacco when it was new, and medicine had not yet shown what it does.
Tobacco is of American origin and was unknown to the early Arabs; it appeared in Muslim lands at the end of the tenth and start of the eleventh century AH (around 1600 CE). The ruling on smoking turns on harm: if the harm the Sharia forbids is established, it is forbidden; if not, it is disliked or allowed. That is why scholars differed about it in the past, as medicine has kept revealing its harms. Since doctors now confirm the severe harm, and the Sharia forbids severe harm, intoxicants and dulling substances, and the wasting of wealth (citing al-Bukhari and Muslim), smoking is a bad habit that is forbidden.
What is known now
Today the harm is beyond doubt. The World Health Organization says tobacco damages nearly every organ in the body. It kills more than 7 million people every year. More than 1.6 million of them never smoked, but breathed in the smoke of others. All forms of tobacco are harmful, the water pipe included, and there is no safe level. Nicotine, it says, is highly addictive and harmful, above all to the young.
Tobacco damages nearly every organ in the body. It kills more than 7 million people each year, including over 1.6 million non-smokers exposed to second-hand smoke. All forms of tobacco use are harmful, waterpipe tobacco among them, and there is no safe level of exposure. Nicotine is highly addictive and harmful, particularly for children and young people.
The Qur'an on harming yourself
The Qur'an says: "make not your own hands contribute to (your) destruction". It says: "Nor kill (or destroy) yourselves". It says the Prophet (ﷺ) allows what is good and pure, and forbids what is bad and impure. And the Prophet (ﷺ) said that God (﷾) dislikes the wasting of wealth. Money spent every day on something that harms the body is wealth wasted.
“And spend of your substance in the cause of Allah, and make not your own hands contribute to (your) destruction; but do good; for Allah loveth those who do good.”
“O ye who believe! Eat not up your property among yourselves in vanities: But let there be amongst you Traffic and trade by mutual good-will: Nor kill (or destroy) yourselves: for verily Allah hath been to you Most Merciful!”
“"Those who follow the messenger, the unlettered Prophet, whom they find mentioned in their own (scriptures),- in the law and the Gospel;- for he commands them what is just and forbids them what is evil; he allows them as lawful what is good (and pure) and prohibits them from what is bad (and impure); He releases them from their heavy burdens and from the yokes that are upon them. So it is those who believe in him, honour him, help him, and follow the light which is sent down with him,- it is they who will prosper."”
Al-Mughira ibn Shu'ba wrote that he heard the Prophet (ﷺ) say that Allah dislikes three things for people: idle talk, the wasting of wealth, and asking too many questions.
A father's question
Today the great majority of scholars hold smoking forbidden, because its harm is certain. In 2005 a father wrote to the Grand Mufti of Egypt, Ali Gomaa. He smoked heavily, he said, and sometimes had to smoke near his small children. The answer was not a lecture. It told him to stop, to protect himself, his children and the people around him. Each of us is responsible for those in our care. That is the heart of the matter: Islam asks a believer to look after the life God (﷾) gave him, and the lives of others.
Smoking is forbidden, as the great majority of scholars hold, because its harm is certain. It cites "no harm and no returning harm", 2:195 and 4:29, and tells a smoker to quit to protect himself, his children and society, since each person is a shepherd responsible for those in his care.
Tobacco is of American origin and was unknown to the early Arabs; it appeared in Muslim lands at the end of the tenth and start of the eleventh century AH (around 1600 CE). The ruling on smoking turns on harm: if the harm the Sharia forbids is established, it is forbidden; if not, it is disliked or allowed. That is why scholars differed about it in the past, as medicine has kept revealing its harms. Since doctors now confirm the severe harm, and the Sharia forbids severe harm, intoxicants and dulling substances, and the wasting of wealth (citing al-Bukhari and Muslim), smoking is a bad habit that is forbidden.
Tobacco damages nearly every organ in the body. It kills more than 7 million people each year, including over 1.6 million non-smokers exposed to second-hand smoke. All forms of tobacco use are harmful, waterpipe tobacco among them, and there is no safe level of exposure. Nicotine is highly addictive and harmful, particularly for children and young people.
Other people, too
Smoking does not harm the smoker alone. Over a million people a year die from smoke they did not choose to breathe. Even a bad smell was enough for the Prophet (ﷺ) to tell those who had eaten raw garlic or onion to keep away from the mosque, so as not to trouble others. How much more a smoke that sickens them.
Tobacco damages nearly every organ in the body. It kills more than 7 million people each year, including over 1.6 million non-smokers exposed to second-hand smoke. All forms of tobacco use are harmful, waterpipe tobacco among them, and there is no safe level of exposure. Nicotine is highly addictive and harmful, particularly for children and young people.
Jabir ibn Abdullah reports that the Prophet (ﷺ) said that whoever has eaten garlic or onion should keep away from the mosque, or stay at home. He himself did not eat a dish with a strong smell, saying that he spoke with those whom they did not speak with.
If you smoke
Nicotine is hard to give up, and a smoker who wants to stop needs help, not scorn. No one has to quit before becoming a Muslim. The Qur'an says to those who have wronged themselves: "Despair not of the Mercy of Allah: for Allah forgives all sins". Ramadan, with its long daylight hours without smoking, can be a first step.
Tobacco damages nearly every organ in the body. It kills more than 7 million people each year, including over 1.6 million non-smokers exposed to second-hand smoke. All forms of tobacco use are harmful, waterpipe tobacco among them, and there is no safe level of exposure. Nicotine is highly addictive and harmful, particularly for children and young people.
“Say: "O my Servants who have transgressed against their souls! Despair not of the Mercy of Allah: for Allah forgives all sins: for He is Oft-Forgiving, Most Merciful.”
Perspectives
Some say it is only disliked
Some Muslims point out that no verse or hadith names tobacco. And some scholars of the past held it only disliked (makruh), not forbidden.
Tobacco is not named in the Qur'an or the hadith. Scholars differed about it when it first came. So, they say, it cannot be called forbidden.
Rebuttal
Those scholars ruled before its harm was known. Their own principle was that the ruling turns on harm. Now that doctors and the World Health Organization have shown the harm beyond doubt, the same principle makes it forbidden, as the great majority of scholars now hold.
It is my own choice
Many people say smoking is a personal choice. An adult may take risks with his own health, they say, and religion has no business forbidding it.
An adult may harm his own health if he chooses, so smoking is no one else's concern.
Rebuttal
Smoking is not a private act. More than 1.6 million people a year die from second-hand smoke. And in Islam a person's life and health are not his to throw away: the Qur'an says, "Nor kill (or destroy) yourselves".
The Islamic perspective
Life and health are a trust from God (﷾). Because the harm of smoking, to the smoker and to others, is now certain, the great majority of scholars hold it forbidden. The Qur'an forbids destroying yourself, and the Prophet (ﷺ) disliked the wasting of wealth. A smoker who wants to stop should be helped, and God's (﷾) mercy is open to him.
The ruling on smoking turns on harm, which is why scholars once differed.
Tobacco kills more than 7 million people a year, over 1.6 million of them non-smokers. There is no safe level.
The Qur'an forbids people to bring about their own destruction.
The great majority of scholars today hold that smoking is forbidden.