A RASH VOW
Zephthah made a vow to the Lord and said, “If You will indeed give me the sons of Ammon into my hand, then it shall be that whatever comes out of the doors of my house to meet me when I return in peace from the sons of Ammon, it shall be the Lord’s, and I will offer it up as a burnt offering. -- Judges 11:30-31
Zephthah, who thought himself about to be taken over by the Ammonites, bartered with God, vowing to give whatever was first out of the doors of his home upon his return as a burnt offering to the Lord, if God would first give him victory over the Ammonites.
After God had lived up to His part of the bargain, Zephthah returned home to be greeted by his daughter, who was the first to come joyously from the door of him home.
When Zephthah came to his house at Mizpah, behold, his daughter was coming out to meet him with tambourines and with dancing. Now she was his one and only child; besides her he had no son or daughter. -- Judges 11:34