Umm Salama, the wife of Allah's Apostle ( صلی اللہ علیہ وسلم ), reported Allah's Messenger ( صلی اللہ علیہ وسلم ) to have said:
He who has a sacrificial animal with him whom (he intends) to offer as sacrifice, and he enters the month of Dhu'I-Hijja, he should not get his hair cut or nails trimmed until he has sacrificed the animal.