There are about 30 biblical references to vows, most of which are from the Old  Testament. The books of Leviticus and Numbers have several references to vows in  relation to offerings and sacrifices. There were dire consequences for the  Israelites who made and broke vows, especially vows to God.

The story  of Jephthah illustrates the foolishness of making vows without understanding the  consequences. Before leading the Israelites into battle against the Ammonites,  Jephthah—described as a mighty man of valor—made a rash vow that he would give  to the Lord whoever first came out of doors to meet him if he returned home as  the victor. When the Lord granted him victory, the one who came out to meet him  was his daughter. Jephthah remembered his vow and offered her to the Lord (Judges 11:29-40).  Whether or not Jephthah should have kept this vow is dealt with in another  article. What this account shows us is the foolishness of rash vows.

Perhaps this is why Jesus gave a new commandment concerning vows. “Again, you  have heard that it was said to the people long ago, ‘Do not break your oath, but  keep the oaths you have made to the Lord.’ But I tell you, Do not swear at all:  either by heaven, for it is God’s throne; or by the earth, for it is his  footstool; or by Jerusalem, for it is the city of the Great King. And do not  swear by your head, for you cannot make even one hair white or black. Simply let  your ‘Yes’ be ‘Yes,’ and your ‘No ,’ ‘No’; anything beyond this comes from the  evil one” (Matthew  5:33-37).

The principle here is clear for Christians: do not make  vows, either to the Lord or to one another. First, we are unable to know for  sure whether we will be able to keep vows. The fact that we are prone to the  errors in judgment which are part of our fallen nature means that we may make  vows foolishly or out of immaturity. Further, we don’t know what the future will  bring—only God does. We don’t know what will happen tomorrow (James 4:14), so to make a vow that we will do or not do  something is foolish. God is the one in control, not us, and He “works all  things together for good for those who love Him and are called according to His  purpose” (Romans  8:28). Knowing this, we can see that it is unnecessary to make vows and that  it indicates a lack of trust in Him. Finally, Jesus commands that our word be  sufficient without making vows. When we say “yes” or “no,” that’s exactly what  we should mean. Adding vows or oaths to our words opens us up to the influence  of Satan whose desire is to trap us and compromise our Christian  testimony.

If we have made a vow foolishly and realized we cannot or  should not keep it, we should confess it to God, knowing that He is “faithful  and just and will forgive us our sins and purify us from all unrighteousness.” A  broken vow, while serious, is not an unforgivable matter if taken to the Lord in  true confession. God will not hold us to vows made imprudently, but He expects  us to obey Jesus and refrain from making vows in the future.