30 And Jephthah made a vow to the LORD, and said, "If You will indeed deliver the people of Ammon into my hands,  31  then it will be that whatever comes out of the doors of my house to meet me, when I return in peace from the people of Ammon, shall surely be the LORD's, and I will offer it up as a burnt offering."... 34  When Jephthah came to his house at Mizpah, there was his daughter, coming out to meet him with timbrels and dancing; and she was his only child. Besides her he had neither son nor daughter.

—Judges 11:30-31 & 34

Judges was a spiritually dark time for Israel.  They failed to cleanse the Promised Land of the pagans who were there when they arrived (as God had commanded.)  The result was recurring lapses into paganism by the Israelites.  Each time the people were at their worst, God sent them a “Judge,” to lead them into revival.  One such judge was Jephthah.

Before Jephthah went to war against the Ammonites he superstitiously made a foolish vow that if God gave him victory, he would sacrifice whatever he saw first upon returning home.  What did He see first?  His only child.  He was immediately devastated at the thought of sacrificing his daughter.  But since a vow (to God, no less) is a vow, (v.39) says, “he carried out his vow with her which he had vowed.”  Did he actually sacrifice his daughter?

Two things are obviously true:  (1) We must keep our vows.  (2) God forbids human sacrifice.

Some say Jephthah did not sacrifice her, but that she was merely disallowed to marry and have children.  Others say Jephthah sacrificed his daughter. 

Which is it?  Answering this question correctly is not a salvation issue, but remembering what dark times the days of the judges were, we shouldn’t be surprised if he did sacrificed her.

We are wise not to make vows without thinking how we will keep them.