Charles Ellicott Commentary Judges 11:30

"And Jephthah vowed a vow unto Jehovah, and said, If thou wilt indeed deliver the children of Ammon into my hand," — Judges 11:30 (ASV)

Jephthah vowed a vow. —This was a practice among all ancient nations, but especially among the Jews (Genesis 28:20–22; 1 Samuel 1:11; 2 Samuel 15:8; Psalms 66:13).