Bible Verses About Vows

Ecclesiates 5:4-6, KJV:
When thou vowest a vow unto God, defer not to pay it; for he hath no pleasure in fools: pay that which thou hast vowed. Better is it that thou shouldest not vow, than that thou shouldest vow and not pay. Suffer not thy mouth to cause thy flesh to sin; neither say thou before the angel, that it was an error: wherefore should God be angry at thy voice, and destroy the work of thine hands?

Deuteronomy 23:21-23, KJV:
When thou shalt vow a vow unto the LORD thy God, thou shalt not slack to pay it: for the LORD thy God will surely require it of thee; and it would be sin in thee. But if thou shalt forbear to vow, it shall be no sin in thee. That which is gone out of thy lips thou shalt keep and perform; even a freewill offering, according as thou hast vowed unto the LORD thy God, which thou hast promised with thy mouth.

Numbers 30:2, KJV
If a man vow a vow unto the LORD, or swear an oath to bind his soul with a bond; he shall not break his word, he shall do according to all that proceedeth out of his mouth.

Acts 5:1-11, ESV
But a man named Ananias, with his wife Sapphira, sold a piece of property, and with his wife's knowledge he kept back for himself some of the proceeds and brought only a part of it and laid it at the apostles' feet. But Peter said, “Ananias, why has Satan filled your heart to lie to the Holy Spirit and to keep back for yourself part of the proceeds of the land? While it remained unsold, did it not remain your own? And after it was sold, was it not at your disposal? Why is it that you have contrived this deed in your heart? You have not lied to men but to God.” When Ananias heard these words, he fell down and breathed his last. And great fear came upon all who heard of it.