But above all, my brothers, do not swear, either by heaven or by earth or by any other oath, but let your “yes” be yes and your “no” be no, so that you may not fall under condemnation.
-James 5:12 ESV
Have you ever got in a situation where you had to make tons and tons of promises in order for someone to believe you? What got you to that point where you had to do that?
I remember when I was a kid my mom told me to clean my room. So I'd sit, and procrastinate, and play with toys, and then mom would say, "I'm checking your room in 5 min!" So me and my brothers would rush and shove everything under the bed and in the closet. We'd then yell to mom, "It's clean!!!" She'd come check the room, and instantly she'd pull everything out from the closet and out from under the bed into the middle of the room. We'd clean it for real the next time, but for whatever reason she didn't believe us... Hmmm.
James understood this. He pretty much said stop the lying. There's no need to swear on anything, or by anything. If your yes' are always yes, and your no's are always no, then you don't need to swear.
Sorry today's blawhg isn't long, but sometimes it's just simple and doesn't need an explanation...