“Above all, my brothers and sisters, do not swear—not by heaven or by earth or by anything else. All you need to say is a simple “Yes” or “No.” Otherwise you will be condemned.” (James 5:12)
James offers good advice to Christians that they not swear by God’s name in order to prove to people that they are telling the truth. There are a couple reasons for this:
1. God is perfect. If you swear by his name and then fail to keep your word 100%, you are maligning his Holy name.
2. If you are a truthful person you shouldn’t need to swear anyway. People will trust your “yes” and your “no.” by swearing in God’s name you are implicitly admitting that your usual “yes” and “no” are not trustworthy.
Reason number two is why I try not to use the word “promise” when I tell other people that I will do something for them. Every word I say, (except in obvious humor) should be a promise.