"And the elders of Gilead said to Jephthah, ‘The Lord will be a witness between us, if we do not do according to your words and the people made him head and commander of them.’ And Jephthah made a vow to the Lord.” Judges11:10, 11, 30; (Paraphrase)

This a story with mingled emotions, where defeat is snatched from the hands of victory. Despite being the son an illegitimate child and kicked out of his home by his half-brothers, Jephthah, the 9th judge, rose through the ranks to become a mighty man of valor (special forces) and ultimately commander-in-chief over the armies of Israel. He led his army to victory over the Ammonites in their land dispute, but in his prayer for victory he made a thoughtless vow to God that upon returning home whatever came out of the door of his home first to greet him, he would offer as a burnt offering to the Lord. Tragically, his daughter and only child was first to greet him. Human sacrifices were strictly forbidden (Deut. 12:31), so he was flat out sinful to have sacrificed his daughter. Be cautious and very selective in making promises to God.