Albert Barnes Commentary Numbers 30:1

"And Moses spake unto the heads of the tribes of the children of Israel, saying, This is the thing which Jehovah hath commanded." — Numbers 30:1 (ASV)

The regulations concerning vows appropriately follow those given for sacrifices, since a large proportion of vows would always relate to the presentation of such offerings. Rules had already been given (Leviticus 27:0) for the valuation of things vowed to God.

It is probable that this new legislation, dealing especially with vows made by persons under guardianship, was prompted by some practical difficulty that had recently arisen. This legislation is addressed by Moses to the heads of the tribes (Numbers 30:1), who, in their judicial capacity, would have to decide questions on these matters.

There is no provision in the chapter for canceling vows made by boys and young men. From this, it has been inferred that the vows of males were binding in all cases and circumstances.