Matthew 5:34-37
34But I say unto you, Swear not at all; neither by heaven; for it is God's throne:
35Nor by the earth; for it is his footstool: neither by Jerusalem; for it is the city of the great King.
36Neither shalt thou swear by thy head, because thou canst not make one hair white or black.
37But let your communication be, Yea, yea; Nay, nay: for whatsoever is more than these cometh of evil.
(KJV)