The Law concerning Vows

301 Then Moses spoke to the heads of the tribes of the sons of Israel , saying , "This is the word which the Lord has commanded . 2 " If a man makes a vow to the Lord , or takes an oath to bind himself with a binding obligation , he shall not violate his word ; he shall do according to all that proceeds out of his mouth .

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.