Numbers 30:1-2

Amplified Bible

The Law of Vows

30 Then Moses spoke to the leaders of the tribes of the Israelites, saying, “This is the thing which the Lord has commanded: ² If a man makes a vow to the Lord or swears an oath to bind himself with a pledge [of abstinence], he shall not break (violate, profane) his word; he shall do according to all that proceeds out of his mouth.