John Gill Commentary Numbers 30:4

"and her father heareth her vow, and her bond wherewith she hath bound her soul, and her father holdeth his peace at her; then all her vows shall stand, and every bond wherewith she hath bound her soul shall stand." — Numbers 30:4 (ASV)

And her father hear her vow, and her bond with which she has
bound her soul
Her vow, which is binding upon her, or her vow and an oath annexed to it; which makes it still more strongly binding; and this he hears himself, or it is reported to him by others: and her father shall hold his peace at her; shall not reprove her for it, nor contradict her in it: then all her vows shall stand; be they what, or as many as they may:

and every bond with which she has bound her soul shall stand ;
his silence being to be interpreted as approving of them, and consenting to them.