Mukhtasar Muslim (Abridged) 1251 — If the first ten days

Umm al-Mu'mineen Umm Salamah (may Allah be pleased with her) reports that the Messenger of Allah (peace and blessings be upon him) said: Whoever has an animal for sacrifice and the crescent of Dhul-Hijjah is sighted, then he should not cut his hair or nails until he has offered the sacrifice.