Rav Shach asks this question on the Rambam.[laws of temura, chapter 4 law 7] If one sanctifies a female sheep to be a Passover sacrifice (and we know a female cannot be a pesah) and it gives birth to a male sheep, both go to pasture. This like the first tana in Temura page 19a. But the Gemara says that this law of the tana is applicable even if the female was pregnant at the time she was sanctified, and the gemara says the reason is because the baby in the womb is part of the mother. (The offspring does not become sanctified separately from the mother.) However, the Rambam decided the law like this tana, and yet also holds that the baby in the womb is not part the mother, so the Rambam should have decided the law is the male lamb can be sacrificed as a Passover like R. Elazar. To answer this question I would like to suggest that in Tmura page 10 there is an argument between R. Yochanan and Bar Pada. There, Bar Pada said holiness does not descend on a baby in the womb. I think the Rambam decided the law to be like Bar Pada. [Therefore, even though the baby is not part of the mother still it cannot be sacrificed as a Passover offering]. {But one can still ask on this because the Rambam says the baby sheep must not be sacrificed as a Passover, while Bar Pada might mean that holiness does not automatically descend on the baby lamb, but that after it is born, it can be sacrificed for whatever one intends it to be.} However, he interprets Bar Padaa to mean that a lamb in the womb can only receive holiness of money not holiness of body. We can see many examples of this in the Rambam for example if one sanctifies a lamb in the womb to be a sin offering. There also the holiness that descends on the lamb in that of moeny.ie it goes to pasture until it receives blemish and is sold and the money is used to buy a sin offering. The question on this would come from the law that the Rambam writes that a lamb in the womb of an animal with a blemish is considered whole and perfect, and can be sacrificed, I think the way people understand the Rambam is that if one sanctifies a female animal to be a peace offering, and then it receives a blemish, then its offspring can still be sacrificed to be a peace offering. But I think the Rambam meant that the offspring can be sacrificed as a peace offering, but not that it is sacrificed as such. Rather one needs to sanctify the offspring after it is born, and then it can be sacrificed as a peace offering. Rav Shach brings the answer of Rav Isaac Zev, but asks on it. And he does not find a better answer. So here I suggest a possible approach to answer this question. So, my approach is this. I am saying the Rambam decided the law like bar pada and that bar pada meant that the holiness of the altar does not come on the lamb but holiness of money does, and not just holiness on money comes on the lamb, but it comes in such a way that it cannot be excused from the altar until it goes to pasture, and gets a blemish, and then is sold, and that money that it is sold for becomes a Passover if it was sold before Passover and a peace offering of after Passover. A proof is that the Gemara itself says exactly this that Bar Pada meant only holiness of the altar does not come on the lamb, for the Gemara asked on Bar Pada from a Mishna that implies holiness can come on the lamb and answers that refers to holiness on money. But even there the Tosphot asks from the end of that Mishna and answers that since holiness of money descends on it, therefore automatically the holiness of body also come on it and that means it is sold and with that money one buys the sacrifice it was meant for. This is exactly how the Rambam decided the law in our case of the female that was sanctified to be a Passover. Then she gives birth to a male lamb. Even though the Rambam decided that the baby in the womb is not part of the mother, still holiness of the altar does not come on it, and it is sold and with that money one buys a Passover sacrifice. This is exactly how Bar Pada is explained in the Gemara and Tosphot and the Shita Mekubetzet, number 16, page 10 of TemuraI saw after writing the above paragraph that Rav Aaron Kotler has an approach that also can answer this question. The question is that the male lamb of a female that was sanctified to be a Passover sacrifice is not sacrificed as a Passover. This is odd because we hold the offspring while in the womb is not part of teh mother and we hold since the holiness of money comes on something then also come the holiness of the body. Rav Aaron hold that last principle works only if it is immediate. but if there is a delay between the holiness of money and holiness of body then holiness if body does not come. ---------------------------------------------------------רב שך asks this question on the רמב’’ם. If one sanctifies a female sheep to be a קרבן פסח (and we know a female cannot be a פסח) and it gives birth to a male sheep, both go to pasture. This like the first תנא in תמורה page י''ט ע''א. But the גמרא says that this law of the תנא is applicable even if the female was pregnant at the time she was sanctified, and the גמרא says the reason is because the וולד in the womb is part of the mother. (The וולד does not become sanctified separately from the mother.) However, the רמב’’ם decided the law like this תנא, and yet also holds that the וולד in the womb is not part the mother, so the רמב’’ם should have decided the law is the male וולד can be sacrificed as a פסח like ר' אלעזר. To answer this question, I would like to suggest that in תמורה page י' there is an argument between ר' יוחנן and בר פדא. There, בר פדא said holiness does not descend on a וולד in the womb. I think the רמב’’ם decided the law to be like בר פדא. [Therefore, even though the וולד is not part of the mother still it cannot be sacrificed as a קרבן פסח. {But one can still ask on this because the רמב’’ם says the וולד must not be sacrificed as a פסח, while בר פדא might mean that holiness does not automatically descend on the וולד ,but that after it is born ,it can be sacrificed for whatever one intends it to be .} However, he interprets בר פדאa to mean that a וולד in the womb can only receive holiness of דמים not holiness of גוף. and we can see many examples of this in the רמב’’ם ,for example if one sanctifies a וולד in the womb to be a sin offering. There also the holiness that descends on the וולד in that of money. i.e. it goes to pasture until it receives blemish, and is sold, and the money is used to buy a sin offering. The question on this would come from the law that the רמב’’ם writes that a וולד in the womb of an animal with a blemish is considered whole and perfect, and can be sacrificed. I think the way people understand the רמב’’ם is that if one sanctifies a female animal to be a peace offering, and then it receives a blemish, then its וולד can still be sacrificed to be a peace offering. But I think the רמב’’ם meant that the וולד can be sacrificed as a peace offering, but not that it is sacrificed as such. Rather one needs to sanctify the וולד after it is born, and then it can be sacrificed as peace offering.So, my approach is this. I am saying the רמב’’ם decided the law like בר פדא and that בר פדא meant that the holiness of the altar does not come on the lamb וולד ,but holiness of דמים does. And not just holiness of דמים come on the lamb, but it comes in such a way that it cannot be excused from the altar (אינו יוצא מידי המזבח לעולם)until it goes to pasture and gets a blemish and then is sold and that money that it is sold for becomes a קרבן פסח if it was sold before קרבן פסח and a peace offering If after Passover. A proof is that the גמרא itself says exactly this that בר פדא meant only holiness of the altar does not come on the lamb, for the גמרא asked on בר פדא from a משנה that implies holiness can come on the lamb and answers that refers to holiness on money. But even there the תוספות asks from the end of that משנה and answers that since holiness of money descends on it, therefore automatically the holiness of body also come on it and that means it is sold and with that money one buys the sacrifice it was meant for. This is exactly how the רמב’’ם decided the law in our case of the female that was sanctified to be a קרבן פסח. Then she gives birth to a male lamb. Even though the רמב’’ם decided that the וולד in the womb is not part of the mother(עובר לאו ירך אמו) , still holiness of the מזבח does not come on it, and it is sold and with that money one buys a קרבן פסח sacrifice. This is exactly how בר פדא is explained in the גמרא and תוספות and the שיטה מקובצת, number ט''ז, דף י' of תמורה ------------------------------------------------------------------ I saw after writing the above paragraph that רב אהרן קטלר has an approach that also can answer this question. The question is that the male lamb of a female that was sanctified to be a Passover sacrifice is not sacrificed as a Passover. This is odd because we hold the וולד while in the womb is not part of the mother and we hold since the holiness of money comes on something,(מיגו דנחתא קדושת דמים נחתא קדושת הגוף) then also come the holiness of the body. רב אהרון hold that last principle works only if it is immediate. But if there is a delay between the holiness of money and holiness of body then holiness if body does not come.