And you must tie them as a sign upon your hand, and they must serve as a frontlet band between your eyes;

(Deut. 6:6-9) In regard to these verses, the Bible commentary by Keil and Delitzsch states:

they were to be bound upon the hand for a sign, and worn as bands (frontlets) between the eyes. . . . these words are figurative, and denote an undeviating observance of the divine commands.”