Read this article:
It is somewhat long but totally worth it!  
 
I make promises to God each morning. Most of the time it is something as simple as, "I promise that I will not eat sweets today" or "I will stay on my eating plan today" or "I promise that my daughter and I will get in a whole day of school". Somtimes the promises are more serious but either way it keep me accountable. I would NEVER want to break a promise to the Lord whereas  would easily break a promise to myself.
 
Well, this morning my Bible reading took me to Chapter 30 in Numbers. It talks about making vows and pledges to God. It also talks about how we are to keep them. The only people that do not have to keep a vow or pledge to God is if a woman is told not to by her father or husband. But, it says that divorced women much keep their pledges (that would be me so I had better keep them). Anyway, Numbers 30:1 comes right out and says that if make a promise to God we must keep it. :) Ecclesiastes 5:4-7 also talks about keeping our promises to God. 
 
One article I read says that we should not make vows to God or to each other. I don't really think that is true. If that were true then no one should get married because that is a vow to each other and to God. So to say that we shouldn't make vows is a little silly to me. I make vows to God every day but I NEVER make vows that I can't keep. Because it is a VERY serious thing to make a vow or promise and then not keep it. That is why I make my vows daily. I never make a promise about tomorrow. I can't. We do not know what will happen tomorrow. I think the ONLY time this is not true is when we are dealing with relationships. I can promise to my best firends that I will be thier friend forever. That is a promise that I will never break. I can promise to my daughter that I will be there for her forever. That is a promise that I know I will never break. But outside of relationships that are very important to us we can NOT make a vow for tomorrow. With God's help we can promise to do or not do soemthing for one day and keep it...but only with God's help is even this possible. 
 
Here are some links about promises and vows (be sure to pray to God that you see and learn what He will have to see an learn before reading any of these as these are just written by people like you and me so we should not lean on them but lean on God and what He wants to teach us through them):