Rujukan Mishnah untuk Bilangan 18:16: Mishnah Bekhorot

[An Israelite] who buys a fetus of a donkey belonging to a non-Jew or who sells one to him, although this is not permitted, or who forms a partnership with him, or who receives [an animal] from him to look after or who gives [his donkey] to him to look after, is exempt from the [law of the] bekhor, for it says: [“I sanctified to me all the firstborn] in Israel,” (Numbers 3:13) but not in non-Jews. Priests and levites are exempt through [an argument made by a] kal vehomer: if they exempted the first-born belonging to the Israelites in the wilderness, it follows all the more so that they should exempt their own.

There is one who is [counted as] a firstborn [with respect to] inheritance but not with respect to redemption from a priest; a firstborn with respect to redemption from a priest but not a firstborn [with respect] to inheritance; a firstborn [with respect to both] inheritance and redemption from a priest; and a firstborn [in respect] to neither inheritance nor redemption from a priest. Which is a firstborn [with respect] to inheritance but not to redemption from a priest? One which follows one which was not viable whose head came forth alive, or one born in the ninth month whose head came out dead, or when a woman aborts something that looks like an animal, beast or bird, the words of Rabbi Meir. But the sages say: [it is not considered an opening of the womb] until [the abortion] has the form of a human being. If [a woman] aborts a sandal or a placenta or a fetus having an articulated shape, or if an embryo came out by pieces, [the infant] which follows after them is a first-born [with respect] to inheritance but not a first-born for redemption from a priest. If one who never had children married a woman who had already given birth, even if she had given birth when she was a slave but is now free, or [had given birth] when she was a non-Jew but has since converted, if after coming to the Israelite she gave birth, [the infant] is considered a first-born [with respect] to inheritance but not a first-born for redemption from a priest. Rabbi Yose the Galilean says: [the infant] is a firstborn [with respect] to inheritance and for redemption from a priest, as it says: “Whatever opens the womb in Israel” (Exodus 13:2), meaning only if it opens the womb in Israel. If one had children already and married a woman who had never given birth previously Or if she converted when pregnant, or if she was freed when pregnant, and she gave birth; If she and a priestess gave birth, she and a Levite’s daughter, she and a woman who had already given birth; And similarly [if a woman] who did not wait three months after her husband's death, married and gave birth and it is not known if the infant was born in the ninth month since the death of the first [husband] or in the seventh month since she married the second, it is a firstborn for redemption from a priest but not a first-born [with respect] to inheritance. Which is a firstborn both [in respect] of inheritance and for redemption from a priest? If [a woman] miscarries a sac full of blood or full of water or full of pieces of flesh; or if [a woman] miscarries something with the shape of fish or locusts or reptiles, or creeping things, or if she discharges on the fortieth day [of conception], [the infant] which follows after [these discharges] is a firstborn both [in respect] of inheritance and for redemption from a priest.

If one woman had given birth before and the other had never before given birth, the two women belonging to two husbands, and they gave birth to two males, the one whose wife had never before given birth gives five selas to the priest. If they gave birth to a male and a female, the priest receives nothing. If the son dies within thirty days although he gave the priest [the five selas], he must return them. If he dies after thirty days, although he has not yet given the five selas, he (the father) must give them. If he dies on the thirtieth day, it is as if he died on the previous day. But Rabbi Akiva says: if he gave [the five selas] he cannot reclaim them, but if he had not yet given, he need not give. If the father dies within thirty days, [the infant] is under the presumption of not having been redeemed until proof is brought that he has been redeemed. If the father dies after thirty days, the infant is under the presumption of having been redeemed until he [the son] is told that he was not redeemed. If both he and his son need to be redeemed, the father takes precedence over his son. Rabbi Judah says: his son comes first for the command to redeem him was upon his father, and the command of his son is upon him.