Nor should you swear by your head, for you cannot make a single hair white or black.
μήτε ἐν τῇ κεφαλῇ σου ὀμόσῃς, ὅτι οὐ δύνασαι μίαν τρίχα λευκὴν ἢ μέλαιναν ποιῆσαι.
