Êxodo 33:23 Halacá: Mishneh Torah, Foundations, Mishneh Torah, Tefillin, Mezuzah and the Torah Scroll & Mishneh Torah, Positive Mitzvot

What was it then that Moses our Master sought to attain when he said: "Show me, I pray Thee, Thy glory" (Ex. 33,18)? He desired to know the truth of the existence of the Holy One, blessed is He! with a thorough knowledge within his heart, even as he would know a certain person whose countenance he saw and whose likeness was imprinted upon his heart, so that he could find him in his mind's vision separated from other persons; even so did Moses our Master seek to establish the existence of the Holy One, blessed is He! separated within his heart from other beings, until he would know the truth of His existence as it is. And He, blessed is He! answered him, that it is not within the intellectual power of the living man, who is a composite being of body and soul, to reach the pure truth of this matter; but He, blessed is He! imparted to him that which no man before him did nor no man after him shall know for, he fathomed the subject of the true existence of the Holy One, blessed is He! even so that He became separated in his mind's vision from other beings; as, for instance, he could separate in his mind a certain person, whose back and body and clothes he saw from bodies of other persons. And, concerning this matter the Passage points, saying: "And thou shalt see My back; but My face shall not be seen" (Ex. 33,23).

The thong of the phylactery for the head is inserted in the loop open at both ends. It is measured to fit the wearer's head, and then tied in a rectangular knot like a Daleth. This knot, every scholar should learn how to make. It is impossible to teach its form by description; this can only be taught by ocular demonstration. In the case of the phylactery for the arm, the thong is tied in a knot in the shape of a Yod. The thong of the phylactery for the arm should move freely in the loop, so that the wearer can loosen or tighten it when he puts it on his arm.

To appear (in the Sanctuary) on the feast, as it is said, “Three times in the year shall all thy males appear (before the Lord thy God in the place which He shall choose)” (Deut. 16:16).