When you make a vow to God, do not delay in fulfilling it. He has no pleasure in fools; fulfill your vow. Ecclesiastes 5:4
Have you ever had a business relationship with someone who made a commitment but later said, "Well, things changed, so I cannot honor our original agreement." Sometimes this may be the case, but often it is simply an opportunity to avoid fulfilling an agreement.
God is big on fulfilling vows. God's nature is righteousness and truth. You will always see God honor His Word. He expects the same of His people.
God says there are consequences when we do not fulfill our vows.
It is better not to vow than to make a vow and not fulfill it. Do not let your mouth lead you into sin. And do not protest to the temple messenger, "My vow was a mistake." (Ecclesiastes 5:5-6).
God tells us that He will destroy the work of our hands for failure to fulfill vows...