If a man vows a vow to the Lord, or swears an oath to bind himself with a bond, he will not break his word. He will do according to all that proceeds out of his mouth.
Or when a person swears by speaking rashly with his lips to do evil or to do good, anything that a man may speak rashly by oath, and he did not realize it, but when he realizes it, then he has become guilty of any of these things.
Behold, on the mountains, the feet of him who brings good news, who proclaims peace! Make your feasts, O Judah, and complete your vows. For the wicked one will never again pass through your midst; he is completely cut down.
Do not trust them. More than forty men, who have bound themselves with an oath to neither eat nor drink until they have killed him, are waiting for him. And now they are ready, waiting for your promise.”
So Jephthah went with the elders of Gilead. The people set him over them as ruler and leader. And Jephthah spoke all his words before the Lord in Mizpah.
At the end of two months she returned to her father, and he did to her according to the vow that he had made. She had not ever slept with a man. So it became a custom in Israel