Short answer
Yes, on the chapter's own words, and the Bible never blames him for it. Jephthah vowed to give the Lord a burnt offering of whatever came out of his door to meet him. His only child, his daughter, came out. Two months later he "did with her according to his vow". He made the vow just after the Spirit of the Lord came upon him. The Law says the Lord hates the burning of sons and daughters, yet no verse condemns Jephthah. The New Testament even names him among its heroes of faith. Islam forbids both the vow and the act. The Prophet (ﷺ) taught that a vow to disobey God (﷾) must not be kept, and the Qur'an says those who kill their children are lost.
Full explanation
The vow and what followed
The Spirit of the Lord came upon Jephthah. Straight after that, he made his vow. He promised a burnt offering, a sacrifice that is burned whole on the altar. The Lord then gave him the victory. His only child came out to meet him, and he said he could not go back on his word.
“Then the Spirit of the Lord came upon Jephthah, and he passed over Gilead, and Manasseh, and passed over Mizpeh of Gilead, and from Mizpeh of Gilead he passed over unto the children of Ammon.”
“And Jephthah vowed a vow unto the Lord, and said, If thou shalt without fail deliver the children of Ammon into mine hands, Then it shall be, that whatsoever cometh forth of the doors of my house to meet me, when I return in peace from the children of Ammon, shall surely be the Lord’s, and I will offer it up for a burnt offering.”
“So Jephthah passed over unto the children of Ammon to fight against them; and the Lord delivered them into his hands.”
“And Jephthah came to Mizpeh unto his house, and, behold, his daughter came out to meet him with timbrels and with dances: and she was his only child; beside her he had neither son nor daughter. And it came to pass, when he saw her, that he rent his clothes, and said, Alas, my daughter! thou hast brought me very low, and thou art one of them that trouble me: for I have opened my mouth unto the Lord, and I cannot go back.”
"According to his vow"
After two months she came back, and he did with her what he had vowed. The daughters of Israel went every year to lament her. The text reports it and passes no judgement on him.
“And he said, Go. And he sent her away for two months: and she went with her companions, and bewailed her virginity upon the mountains. And it came to pass at the end of two months, that she returned unto her father, who did with her according to his vow which he had vowed: and she knew no man. And it was a custom in Israel, That the daughters of Israel went yearly to lament the daughter of Jephthah the Gileadite four days in a year.”
How the story was read in the first century
Josephus, a Jewish historian of the first century, read the chapter plainly. He wrote that Jephthah offered his daughter as a burnt offering, an offering neither agreeable to the Law nor acceptable to God (﷾).
Retelling Judges 11 in the first century, Josephus says that when the two months were over Jephthah sacrificed his daughter as a burnt offering, and he calls it an offering neither agreeable to the law nor acceptable to God.
What the Law says about burning children
The Law of Moses calls the burning of sons and daughters an "abomination", a hateful thing that the Lord hates. In the Book of Jeremiah, God (﷾) says He never commanded it and it never entered His mind.
“Thou shalt not do so unto the Lord thy God: for every abomination to the Lord, which he hateth, have they done unto their gods; for even their sons and their daughters they have burnt in the fire to their gods.”
“And they have built the high places of Tophet, which is in the valley of the son of Hinnom, to burn their sons and their daughters in the fire; which I commanded them not, neither came it into my heart.”
Jephthah in the New Testament
Hebrews, a letter in the New Testament, lists Jephthah by name with Samson, David and Samuel. It says these men did great things "through faith". It gives no word of blame for his vow.
“And what shall I more say? for the time would fail me to tell of Gedeon, and of Barak, and of Samson, and of Jephthae; of David also, and Samuel, and of the prophets: Who through faith subdued kingdoms, wrought righteousness, obtained promises, stopped the mouths of lions,”
A vow to do wrong is not kept
The Prophet (ﷺ) taught that a vow to disobey Allah (﷾) must not be carried out. So no Muslim could be bound by a vow like Jephthah's. The Qur'an names the killing of children a great sin and says that those who slay them are lost. The Qur'an's story of Abraham is different. Allah (﷾) tested him through a vision, then called out to him and ransomed his son with a great sacrifice. The test was stopped by Allah (﷾) Himself, and no child was killed.
Aisha reports that the Prophet (ﷺ) said: whoever vows to obey Allah should keep that vow and obey Him, and whoever vows to disobey Allah must not disobey Him.
“Kill not your children for fear of want: We shall provide sustenance for them as well as for you. Verily the killing of them is a great sin.”
“Lost are those who slay their children, from folly, without knowledge, and forbid food which Allah hath provided for them, inventing (lies) against Allah. They have indeed gone astray and heeded no guidance.”
“Then, when (the son) reached (the age of) (serious) work with him, he said: "O my son! I see in vision that I offer thee in sacrifice: Now see what is thy view!" (The son) said: "O my father! Do as thou art commanded: thou will find me, if Allah so wills one practising Patience and Constancy!"”
“So when they had both submitted their wills (to Allah), and he had laid him prostrate on his forehead (for sacrifice), We called out to him "O Abraham! "Thou hast already fulfilled the vision!" - thus indeed do We reward those who do right. For this was obviously a trial- And We ransomed him with a momentous sacrifice:”
Verse by verse
Judges 11:38-40 — Nevi'im, Shoftim, chapter 11, verses 38-40
“And he said, Go. And he sent her away for two months: and she went with her companions, and bewailed her virginity upon the mountains. And it came to pass at the end of two months, that she returned unto her father, who did with her according to his vow which he had vowed: and she knew no man. And it was a custom in Israel, That the daughters of Israel went yearly to lament the daughter of Jephthah the Gileadite four days in a year.”
Cited for
She mourned her virginity and "knew no man". Jephthah gave her to God's service for life, unmarried. He did not kill her.
The response
The vow was "I will offer it up for a burnt offering", and a burnt offering is burned on the altar. The text says he did with her "according to his vow". The women of Israel then mourned her every year. Josephus, in the first century, read it as a sacrifice. Some read the "and" in verse 31 as "or", so that a person would be dedicated and an animal burned. But the vow was one promise about "whatsoever cometh forth of the doors of my house to meet me". Whatever came out "shall surely be the Lord's, and I will offer it up for a burnt offering".
Where it lands — The chapter's own words, a burnt offering kept according to the vow, describe a death.
Hebrews 11:32-33 — Epistle to the Hebrews, chapter 11, verses 32-33
“And what shall I more say? for the time would fail me to tell of Gedeon, and of Barak, and of Samson, and of Jephthae; of David also, and Samuel, and of the prophets: Who through faith subdued kingdoms, wrought righteousness, obtained promises, stopped the mouths of lions,”
Cited for
Hebrews praises Jephthah's faith in battle, as it praises Samson, without approving his vow.
The response
Hebrews gives no word of blame, and neither does Judges. The Spirit of the Lord came on Jephthah just before the vow, and the Lord gave him the victory just after it. No verse blames him by name, and the only verdict it gives him is praise.
Where it lands — No verse condemns Jephthah by name, while the Law condemns what he did.
Perspectives
Christian readings
Many Christian commentators hold that Jephthah gave his daughter to lifelong service to God, unmarried, and did not kill her. Others accept that she died. They say Hebrews praises Jephthah's faith in battle, not his vow.
The chapter stresses that she "bewailed her virginity" and "knew no man". Some read this as a life of dedicated virginity rather than death.
Rebuttal
The text does mention her virginity. But the vow was a burnt offering, and the chapter says he did with her "according to his vow". Josephus, in the first century, read it as a sacrifice.
Hebrews honours the faith of flawed men such as Samson and Jephthah without approving everything they did.
Rebuttal
Hebrews does honour men who were not perfect. But it gives no word of blame, and neither does Judges. No verse blames him by name, and the only verdict it gives him is praise, while its Law condemns the act.
The Islamic perspective
The Bible records a human sacrifice made to God (﷾) under a vow. It praises the man who made it, and elsewhere calls the same act an abomination. Islam forbids both the vow and the act. The Prophet (ﷺ) said a sinful vow is not to be kept, and the Qur'an condemns the killing of children. Abraham's test was stopped by Allah (﷾) Himself, and his son was ransomed (37:107).
Jephthah vowed a burnt offering to the Lord and did with his only daughter "according to his vow".
The vow came straight after the Spirit of the Lord came upon him. And the Lord then gave him victory.
The Law calls the burning of sons and daughters an abomination that the Lord hates.
Hebrews names Jephthah among the heroes of faith and says nothing against his vow.
Josephus was a Jewish historian of the first century. He retold the story, and says Jephthah sacrificed her as a burnt offering.
In Islam, a vow to disobey Allah (﷾) must not be kept. And the killing of children is a great sin.
In the Qur'an, Abraham was tested through a vision, and Allah (﷾) stopped him. His son was ransomed with a great sacrifice.