Exodus 13:9 - Ellicott's Commentary On The Whole Bible

(9) It shall be for a sign unto thee upon thine hand, and for a memorial between thine eyes. — The practice of wearing tephillin, or “phylacteries,” is referred by the Jews themselves to the time of the Exodus, and regarded by them as resting on the present passage, together with Deuteronomy 6:8; Deuteronomy 11:18. These phylacteries consist of small strips of parchment, on which are written certain passages from the Law — viz., Exodus 13:2-10; Deuteronomy 6:4-9, and Deuteronomy 11:13-21 — and which are then folded tight, placed in small boxes, and attached by bands to the left wrist and the forehead at the hours of prayer. It is well known that a similar custom prevailed in Egypt (Wilkinson, Ancient Egyptians, vol. iii., p. 364); and this has been made an objection to the Mosaic institution of phylacteries, since Moses, it has been thought, would not have encouraged an Egyptian superstition. But the adoption of Egyptian customs, purged from their superstition, is quite in the spirit of the Mosaic institutions, and in no way reprehensible. If the Israelites were addicted to wearing amulets, like the Egyptians, it would have been a wise proviso to substitute for the magic charms of sorcerers the solemn words of the Law, and in this way to turn a current superstition to a good account. The Law was thereby honoured, and the special passages selected would come to be generally known to those who wore them, and to be “in their mouth” and “in their heart” (Deuteronomy 11:18). [Dean Plumptre notices, in his Commentary on the Temptation (St. Matt.), that our Blessed Lord used against the adversary quotations from the Scriptures forming these very Tephillin.]