James 5:12

But above all things, my brethren, swear not, neither by heaven, nor by the earth, nor by any other oath; but let your yea be yea, and your nay nay, lest ye fall into condemnation.

Matthew 5:33-34

Again, ye have heard, that it was said to them of old time, Thou shalt not forswear thyself, but shalt perform thine oaths unto the Lord.

Treasury of Scripture Knowledge

Summary

And ye shall not swear by my name falsely, neither shalt thou profane the name of thy God: I am the LORD.

Bible References

Ye shall

Matthew 5:33
Again, ye have heard, that it was said to them of old time, Thou shalt not forswear thyself, but shalt perform thine oaths unto the Lord.
James 5:12
But above all things, my brethren, swear not, neither by heaven, nor by the earth, nor by any other oath; but let your yea be yea, and your nay nay, lest ye fall into condemnation.