A vow is a promise to God to do something specific for His sake, and it is a very effective way to lift yourself up spiritually and to insert discipline into your religious life. God has given us the power, by our spoken vow, to obligate ourselves like at Mount Sinai. For when you make a vow, a solemn promise to God that you will do something, you are obligated equally as with the commandments given on Mount Sinai. . . .

On the one hand, you can use vows to strengthen yourself when you are in a low state and in danger. On the other hand, you can also use them when you are in a higher state of consciousness, to prepare yourself for the temptations you will face later.

Yitzhak Buxbaum in Jewish Spiritual Practices