The Law concerning Vows
301 Moses spoke to the heads of the tribes of the People of Israel: "This is what God commands: 2 When a man makes a vow to God or binds himself by an oath to do something, he must not break his word; he must do exactly what he has said.
Matthew Henry's Commentary on Numbers 30:1-2
Commentary on Numbers 30:1-2
(Read Numbers 30:1-2)
No man can be bound by his own promise to do what he is already, by the Divine precept, forbidden to do. In other matters the command is, that he shall not break his words, through he may change his mind.