Matthew 5:37

But let your "Yes' be "Yes,' and your "No,' "No.' For whatever is more than these is from the evil one.

Surrounding context

5:36 Nor shall you swear by your head, because you cannot make one hair white or black.

5:37 But let your "Yes' be "Yes,' and your "No,' "No.' For whatever is more than these is from the evil one.

5:38 "You have heard that it was said, "An eye for an eye and a tooth for a tooth.'

Translation and sources