Midrash su Deuteronomio 12:6

(Exodus 13:2) "in man and beast he is Mine": Whatever obtains with the man obtains with his beast. This excludes (from the law of bechor) the Levites, i.e., since it does not obtain with the man, it does not obtain with his beast. Variantly: The bechor of a man is likened to the bechor of a beast, and the bechor of a beast to the bechor of a man. Just as with a beast, a miscarriage (of the first pregnancy) exempts (the second fetus) from (the law of) the bechor, so, with men. And just as with the bechor of a man, one may give it to the Cohein wherever he wishes, so, with the bechor of a beast. From (Devarim 12:6) "And you shall bring there (to the Temple) your burnt-offerings and your sacrifices, etc.", I might think that even if he was far away he must bring it (his first-born) to the Temple. It is, therefore, written "in man and beast he is Mine." The bechor of a man is hereby likened to the bechor of a beast. Just as the latter may be given to a Cohein wherever he wishes, so, the former. And just as the bechor of a man must be cared for for thirty days (before being given to the Cohein), so, the bechor of a beast.

A firstborn human must be redeemed when thirty days old;¹³Firstborn boys are redeemed through the pidyon ha-ben ceremony at the end of thirty days. As indicated above, those born by Caesarean section are exempt. if it survives less than this it is considered a premature child and is exempt from this regulation. The firstborn beast must be redeemed on the eighth day; if it survives less than this it is considered a premature birth. In reference to a human, it is written: And their redemption money—from a month old shalt thou redeem them (Num. 18:16), while in regard to beasts, it is written: But from the eighth day and henceforth it may be accepted (Lev. 22:27). That is, after one is able to lead it to the Temple, since it is said: And thither you shall bring your burnt offerings (Deut. 12:6). In the case of the firstborn of your flock and herds, Scripture says: Thou shalt redeem. This implies that one may redeem the offering from the priest whenever (he wishes). (But if that is so)¹⁴Etz Joseph omits the parenthesized words. Why does the Scripture say: Thou shalt sanctify to the Lord? So that you receive a reward for so doing. But even if you should not sanctify it, it is consecrated, nevertheless, to the Lord, since as Scripture says: It is mine. Why then does Scripture decree Thou shalt sanctify it? In order that you may be rewarded for doing so (voluntarily).

(Exodus 22:29) "Thus shall you do with your ox": Just as with the first-born of an ox, miscarriages exempt (the next birth) from (the laws of) the first-born, so, with the first-born of a human being. Just as with the first-born of a human being you are permitted to redeem the first-born through any Cohein, wherever you wish, so, with the first-born of a beast, you are permitted to give it to any Cohein wherever you wish. Because it is written (Devarim 12:6) "And you shall bring there your burnt-offerings and your sacrifices … and the first-born of your herds and flocks," I might think that he must bring them (the first-born) to the Temple; it is, therefore, written (Exodus 13:2) "in man and beast, he (the first-born) is mine." The first-born of a beast is likened to the first-born of a human being, and the first-born of a human being, to the first-born of a beast. Just as with the first-born of a human being, you look after it for thirty days (before redeeming it), so, with the first-born of a beast, you look after it for thirty days (before giving it to the Cohein.)