عَنْ أُمِّ سَلَمَةَ رَضِيَ اللَّهُ عَنْهَا عَنِ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ قَالَ إِذَا دَخَلَتِ الْعَشْرُ فَأَرَادَ رَجُلٌ أَنْ يُضَحِّيَ فَلَا يَمَسَّ مِنْ شَعْرِهِ وَلَا مِنْ بَشَرِهِ
It is narrated from Sayyida Umm Salama (may Allah be pleased with her) that the Noble Prophet (peace and blessings be upon him) said: When the first ten days of Dhul-Hijjah begin, then a person who intends to offer a sacrifice should neither touch his hair nor his body.