The dedication of every first-born Israelite male baby was to take place after the nation had entered the Promised Land ( Exodus 13:5; Exodus 13:11-12). This was to be a memorial of God"s redemption from Egyptian slavery, as were the feasts of Passover and Unleavened Bread (cf. Exodus 12:14). However, God took the Levites for His special possession in place of the first-born. This happened at Mt. Sinai ( Numbers 3:12-13). Consequently this dedication never took place, but the Israelites did circumcise their sons and observe the Passover when they first entered the Promised Land ( Joshua 5:4-7). [source][source][source]
God may or may not have intended that the Jews should literally wear the "phylacteries" (lit. frontlet-bands, or head-bands, Exodus 13:16; Heb. tephilin). [source][source][source]
"The line of thought referred to merely expresses the idea, that the Israelites were not only to retain the commands of God in their hearts, and to confess them with the mouth, but to fulfil them with the hand, or in act and deed, and thus to show themselves in their whole bearing as the guardians and observers of the law. As the hand is the medium of action, and carrying in the hand represents handling, so the space between the eyes, or the forehead, is that part of the body which is generally visible, and what is worn there is worn to be seen. This figurative interpretation is confirmed and placed beyond doubt by such parallel passages as Prov. iii3 , "Bind them (the commandments) about thy neck; write them upon the tables of thine heart" (cf. Exodus 13:21-22, iv21 , vi21 , 22 , vii3)." [1][source]
"For two thousand years and more, observant Jews have taken those passages literally. The paragraphs that form their contexts ( Exodus 13:1-16; Deuteronomy 6:4-9; Deuteronomy 11:13-21) are written on four strips of parchment and placed in two small leather boxes, one of which the pious Jewish man straps on his forehead and the other on his left arm before he says his morning prayers. The practice may have originated as early as the period following the exile to Babylon in586 B.C. [source][source][source]
"It hardly needs to be said that there is nothing inherently wrong with such a custom. The boxes, called "phylacteries" are mentioned in Matthew 23:5, where Jesus criticizes a certain group of Pharisees and teachers of the law for wearing them. Our Lord, however, condemns not the practice as such but the ostentatious use of "wide" phylacteries as part of a general statement about those who flaunt their religiosity in public: "Everything they do is done for men to see."[source]
"But although the proper and modest use of phylacteries might be spiritually legitimate, it is probably best to understand the references from Exodus and Deuteronomy as figures of speech, since similar statements are found elsewhere in the Old Testament." [2][source]