Wyjścia 34:19 Midrasz: Midrash Tanchuma, Mekhilta DeRabbi Yishmael & Shemot Rabbah

Sanctify unto me all the firstborn (Exod. 13:2). This verse illustrates one of the thirteen rules by which the Torah is interpreted.¹²R. Ishmael’s thirteen hermeneutical rules; see also above, n. 10. A general statement requires a particular statement for its interpretation. Sanctify unto Me all the first born is the general statement which includes both male and female. Does this mean, however, that all firstborn, whether male or female, are to be considered as the firstborn? No, for Scripture adds: The firstling males that are born of thy herds and thy flock thou shalt sanctify (Deut. 15:19), thereby specifying males and not females. It may be possible to maintain on the basis of this verse that a fetus extracted by a Caesarean operation is also to be considered a firstborn. Hence the Scripture states: All that openeth the womb is Mine (Exod. 34:19). That is, a male that opens the womb (through natural birth). Both of men and beast. The firstborn of humans are likened to the firstborn of beasts. Just as the birth of a premature beast releases the one born after it from the law of the firstborn, so a firstborn human being, following a miscarriage, is released from the law of the firstborn. The Levites are not included in this commandment because they are not subject to the law of the firstborn whether of man or of beast.

"Sanctify unto Me every first-born" — generic (implying both males and females). (Devarim 15:19) "the male" — specific, (excluding females). If I have the generic, why do I need the specific? For if I read the generic without the specific, I would assume that anything born first is a "bechor," whether male or female. It is, therefore, written "… the male" — males, but not females. If I have the specific, why do I need the generic? For if I read the specific without the generic, I would assume that any male, whether or not he opens the womb (first) is a "bechor." It is, therefore, written "Sanctify unto Me every bechor, the opener of the womb" — he must be both male and the opener of the womb, as it is written (Exodus 34:19) "All firstlings of the womb are Mine, and (of) all of your kine that bears a male, etc."

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.