James 5:12

Above all, my brothers, never swear an oath, either by heaven or by earth or by anything else; let your "yes" be a plain "yes," your "no" a plain "no," lest you incur judgment.

Matthew 5:33-34

Once again, you have heard how the men of old were told, 'You must not forswear yourself but discharge your vows 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
Once again, you have heard how the men of old were told, 'You must not forswear yourself but discharge your vows to the Lord'.
James 5:12
Above all, my brothers, never swear an oath, either by heaven or by earth or by anything else; let your "yes" be a plain "yes," your "no" a plain "no," lest you incur judgment.