(7) Chapter: When the first ten days of Dhul-Hijjah begin, it is forbidden for the one who wants to offer a sacrifice to remove anything from his hair, nails or skin
Umm Salama reported (these words) directly from Allah’s Messenger (ﷺ):
If anyone has in his possession a sacrificial animal to offer as a sacrifice (on ‘Id al-Adha), he should not get his hair cut and nails trimmed after he has entered the first days of Dhu’l Hijja