Matthew 5:33-37

33 "Again, you have heard that our fathers were told, `Do not break your oath,' and `Keep your vows to ADONAI.'

34 But I tell you not to swear at all -- not `by heaven,' because it is God's throne;

35 not `by the earth,' because it is his footstool;p and not `by Yerushalayim,' because it is the city of the Great King.

36 And don't swear by your head, because you can't make a single hair white or black.

37 Just let your `Yes' be a simple `Yes,' and your `No' a simple `No'; anything more than this has its origin in evil.