Another interpretation: “Consecrate to Me every firstborn” – Rabbi Neḥemya says: The Holy One blessed be He said to Israel: ‘When you come to the land, transfer “the first issue of the womb to Me”’ (Exodus 34:19).15In Exodus 13:11–12 it says: “When the Lord brings you into the land of the Canaanites, as He swore to you and to your forefathers, and He shall give it you, you shall transfer the first issue of the womb to the Lord.”
Could it be that they should not transfer it immediately?16Does the mitzva of the consecration of the firstborn begin only once they enter the Land? The verse states: “You shall transfer the first issue of the womb to the Lord.” The Holy One blessed be He cautioned them [to consecrate the firstborn] immediately because He had spared them in Egypt. “And when your son asks you tomorrow, saying: What is this?
You shall say to him: With strength of hand the Lord brought us out from Egypt, the house of bondage” (Exodus 13:14). “And when your son asks you tomorrow” – inform him of the miracles that were performed on your behalf in Egypt when Pharaoh resisted letting you go, as it is stated: “It was when Pharaoh resisted” (Exodus 13:15). Make it a sign on your hand and on your head, as it is stated: “It will be a sign on your hand, [and as an ornament between your eyes] (Exodus 13:16).
It is analogous to a king who made a great celebration for his daughter who had been taken by enemies. Her father said to her: ‘Make the same celebration that I made for you: A crown on your head, so that you will not forget it.’ So, God performed miracles on Israel’s behalf, and for their sake killed the firstborn of Egypt. He therefore cautioned them regarding the sanctity of the firstborn, who he had killed with His own hands, as it is stated: “The Lord smote every firstborn” (Exodus 12:29). There should be a crown17Phylacteries. on the head of Israel so that they never forget the miracle.