He rent his clothes. — Comp. Joshua 7:6. By one of the curious survivals which preserve customs for centuries after the meaning is gone out of them, every Jew on approaching to Jerusalem for the first time has to submit to the krie — i.e., to a cut made in his sleeve, as a sort of symbol of rending his clothes.
Thou hast brought me very low. — Literally, crushing, thou hast crushed me.
I have opened my mouth unto the Lord. — A vow was not deemed binding unless it had been actually expressed in words (Numbers 30:2-3; Numbers 30:7; Deuteronomy 23:23). There were two kinds of vows among the Hebrews — the simple vow, neder (Leviticus 27:2-27), and the “devotion,” or “ban,” cherem (Leviticus 27:28-29). Anything devoted to Jehovah by the cherem was irredeemable, and became “a holy of holies” (kodesh kadashim) to Him, and was to be put to death (Leviticus 27:29).
I cannot go back. — Numbers 30:2. Jephthah had not understood until now the horror of human sacrifice. He would neither wish nor dare to draw back from his cherem (Ecclesiastes 5:4-5; Matthew 5:33; Jonah 2:9; Pss. 72:25, Psalms 26:11) merely because the anguish of it would fall so heavily upon himself. The Hebrews had the most intense feeling about the awfulness of breaking an oath or vow, and they left no room for any mental reservations (Leviticus 27:28-29). Saul was determined to carry out his ban even at the cost of the life of his eldest son, and even Herod Antipas felt obliged to carry out his oath to Herodias, though it involved a deep pang and a haunted conscience. It is clear that not for one moment did it occur to Jephthah to save himself from the agony of bereavement by breaking his ‘ban” (cherem) as a mere redeemable vow (neder). The Jews shared in this respect the feelings of other ancient nations. Thus the Greeks believed that the house of Athamas were under an inexpiable curse, because when the Achæans had been bidden to offer him up for a sacrifice for compassing the death of Phryxus, Kytissorus, the son of Phryxus, had intercepted the sacrifice (Herod. vii. 197, § 3; Plat. Minos, 5). It must be remembered that though his cherem had taken an unusual and unlawful (though far from unknown) form, the notion of such a vow would come far more naturally to a people which in very recent times, as well as afterwards, had devoted whole cities — men, women, children, cattle, and goods — to absolute destruction (Numbers 21:2-3).