Confession of Faith
Chapter 22: Of Lawful Oaths and Vows
A vow is of the like nature with a promissory oath, and ought to be made with the like religious care, and to be performed with the like faithfulness.1
And the Lord will make himself known to the Egyptians, and the Egyptians will know the Lord in that day and worship with sacrifice and offering, and they will make vows to the Lord and perform them.
When you vow a vow to God, do not delay paying it, for he has no pleasure in fools. Pay what you vow. It is better that you should not vow than that you should vow and not pay. Let not your mouth lead you into sin, and do not say before the messenger that it was a mistake. Why should God be angry at your voice and destroy the work of your hands?
So will I ever sing praises to your name,
as I perform my vows day after day.
I will come into your house with burnt offerings;
I will perform my vows to you,
that which my lips uttered
and my mouth promised when I was in trouble. (ESV)