Numbers 30:13

Every vow, and every binding oath to afflict the soul, her husband may establish it, or her husband may make it void.

Ver. 13. To afflict her soul.] This is one instance of what she may vow. She may curb wanton flesh from the use of things lawful in themselves, but harmful to her, and that by a vow, as did the Rechabites, Jer 35:8-10 which the devil seeing will despair; for vows are as exorcisms to allay our rebellious spirits, and as cords to hamper our treacherous hearts, when they would slip the collar, and decline the yoke. In short, a man may lawfully vow a thing that is either a part of God's worship - as to fast once a month before the sacrament, to pray so many times a day, &c. - or a furtherance thereof, - as to found a lecture, build a college, school, almshouse, give so much weekly to the poor, &c.