Matthew 5:36 in the King James Version
Neither shalt thou swear by thy head, because thou canst not make one hair white or black.
Context
35 nor by the earth, for it is the footstool of his feet; nor by Jerusalem, for it is the city of the great King.
36 Neither shall you swear by your head, for you can’t make one hair white or black.
37 But let your ‘Yes’ be ‘Yes’ and your ‘No’ be ‘No.’ Whatever is more than these is of the evil one.