Is it permissible for a man to sit and cut his nails after assuming Ihram (ritual state for Hajj and ‘Umrah) at the Miqat (site for entering the ritual state for Hajj and ‘Umrah)
or is it only permissible after slaughtering the sacrificial animal?
There is no harm in cutting nails before assuming Ihram, unless he wants to offer a sacrifice and the month of Dhul-Hijjah has begun. Under these circumstances it is not permissible, as the Messenger (peace be upon him) prohibited this. As for doing this after assuming Ihram, that is, after making the intention to assume Ihram, it is not permissible at all, as a Muhrim (pilgrim in the ritual state for Hajj and ‘Umrah) is not allowed to cut their nails or remove any of their hair, until they have finished the Tawaf (circumambulation around the Ka‘bah) and Sa‘y (going between Safa and Marwah during Hajj) in ‘Umrah, after which they remove their Ihram by shaving their hair or cutting it. The same applies to Hajj; after throwing pebbles at Jamarat-ul-‘Aqabah (the closest stone pillar to Makkah), it becomes permissible to shave or cut the hair - shaving is better - and then end the Ihram, either before or after the slaughtering - but it is better after the slaughtering, if possible.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.