Matthew 5:36

36Neitherμήτεbyἐνtheτῇheadκεφαλῇof youσουshall you swearὀμόσῃς,becauseὅτιnotοὐyou are ableδύνασαιoneμίανhairτρίχαwhiteλευκὴνto makeποιῆσαιorἢblackμέλαιναν.

Nor may you swear by your head, because you are not able to make one hair white or black.