It is very important to note that if anyone wants to offer a sacrifice and the month of Dhul Hijjah has begun, then it is haram for him to remove any of his hair, nails, or skin until he has slaughtered the sacrifice. This is based on the hadith of Umm Salamah (may Allah be pleased with her), according to which the Prophet (peace and blessings be upon him) said: “When you see the new moon of Dhul Hijjah…—or according to another version, When the ten days (of Dhul Hijjah) begin and any of you wants to offer a sacrifice, let him refrain (from cutting) his hair and nails” (Ahmad and Muslim).
If the person who wants to offer the sacrifice does remove something from his hair, nails, or skin, then he has to repent to Allah and not do it again, but he does not have to offer any expiation, and that does not prevent him from offering the sacrifice as some common people think, and his sacrifice will be accepted.
In this regard, the late Sheikh Ibn `Uthaymeen, issued the following fatwa:
Yes, his sacrifice will be accepted. With regard to a widespread belief among the common people that if a man removes anything from his hair, nails, or skin during the first ten days of Dhul Hijjah, his sacrifice is not valid, this is not correct, because there is no connection between the validity of his sacrifice and removing anything from these three things.
Responding to a similar question, the late Sheikh Ibn Baz, the former Mufti of Saudi Arabia, stated:
If the person who wants to offer the sacrifice does remove something from his hair, nails, or skin, then he has to repent to Allah and not do it again, but he does not have to offer any expiation, and that does not prevent him from offering the sacrifice as some common people think. If he does any of those things out of forgetfulness or ignorance, or some hair falls unintentionally, then there is no sin on him. If he needs to remove anything he may do so, and there is no blame on him, such as if a nail breaks and it annoys him, so he cuts it, or if a hair gets in his eye and he removes it, or he needs to cut his hair in order to treat a wound and so on.