In Genesis 28:20, 'he vowed a vow' means that there was a desire that what is wished for may come about, thus that the Lord may provide it. Within a vow, something of a bargain is present, and at the same time on man's part, something of a bounden duty to keep his side of it, should he obtain his desire.

(Verweise: Arcana Coelestia 3732)