James 5:12

Above all, my brothers, do not swear an oath, either by heaven or by the earth, or by anything else; let your "Yes" be a plain Yes, and your "No" a plain No, or you will fall under condemnation.

Matthew 5:33-34

"Again, you have heard that the men of old were told, 'You shall not swear falsely, but you must fulfil your oaths to 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, you have heard that the men of old were told, 'You shall not swear falsely, but you must fulfil your oaths to the Lord.'
James 5:12
Above all, my brothers, do not swear an oath, either by heaven or by the earth, or by anything else; let your "Yes" be a plain Yes, and your "No" a plain No, or you will fall under condemnation.