The Gemara in Bechoros (53b) discusses if one is allowed to make a blemish in all the animals in his flock, to avoid being obligated in separating ma’aser behamah (the obligation to offer up every tenth sheep as a korban). The Gemara concludes that doing so is forbidden as, מהרה יבנה בהמ״ ק – “we hope that the Beis HaMikdosh will be speedily rebuilt”, and we need animals fit to be used as korbonos. Nevertheless, Tosfos (Bechoros 33b, d.h. ba’al mum) says: If one makes a blemish in an animal which is kodshim nowadays, he doesn’t violate any issur de’O’raisa [Torah level prohibition], as the animal isn’t fit to be used for anything, לא לגופיה ולא לדמיה – “neither the animal itself, or its value.”
The Chasam Sofer (Shu”t Yoreh De’ah 306) asks: Why is this different to the case of the nozir where we are worried for the arrival of Moshiach every single day? If we are worried that Moshiach may arrive any day, then we should be worried that the firstborn animal may be offered up today and it should be forbidden to make a blemish in it? Moreover, מקריבים אע ״פ שאין בית – “nowadays we can offer up korbonos even though we don’t have a Beis HaMikdosh”, and if we would get permission from the correct people to build a mizbayach [alter] then we would be able to bring korbonos tzibbur [communal offerings] today, as tumah hutrah betzibbur [if an entire community is tomei, communal korbonas may be brought in a state of tumah]?
The Shu”t L’Horas Nossan (Vol. 5, 59 s.k. 18) answers: The Rambam allows Kohanim to drink wine nowadays, because as long as the Beis HaMikodosh hasn’t been rebuilt and Kohanim don’t know which mishmor they belong to, the obligation to perform the avodah isn’t incumbent upon them. Although by drinking wine it may cause them to be disqualified from carrying out the avodah, at this moment in time when they are drinking there is no obligation. Similarly, when it comes to making a blemish in a first-born animal, since at this moment in time there is no Beis HaMikdosh, and we can’t offer up firstborn animals, it’s like the time for the mitzvah hasn’t yet arrived, and there is nothing wrong with circumventing oneself from fulfilling a mitzvah, if one does it before the time of the mitzvah arrives. However, when it comes to the case of the nozir who accepted upon himself nezirus the day Ben Dovid arrives, the issue is not that he is circumventing himself from carrying out a mitzvah, rather, the issue is that if he comes to drink wine, he may end up violating his nezirus if Moshiach arrives that day.
