Hadith 507960
Chapter 20: Hajj - كتاب الحج
وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ عَلْقَمَةَ بْنِ أَبِي عَلْقَمَةَ، عَنْ أُمِّهِ، أَنَّهَا قَالَتْ سَمِعْتُ عَائِشَةَ، زَوْجَ النَّبِيِّ صلى الله عليه وسلم تُسْأَلُ عَنِ الْمُحْرِمِ أَيَحُكُّ جَسَدَهُ فَقَالَتْ نَعَمْ فَلْيَحْكُكْهُ وَلْيَشْدُدْ وَلَوْ رُبِطَتْ يَدَاىَ وَلَمْ أَجِدْ إِلاَّ رِجْلَىَّ لَحَكَكْتُ .
Yahya related to me from Malik from Alqama ibn Abi Alqama that his mother said, "I heard A'isha, the wife of the Prophet, may Allah bless him and grant him peace, being asked whether some one in ihram could scratch their body or not, and she said, 'Yes, he can scratch it and do so as hard as he pleases. I would scratch even if my hands were tied and I could only use my feet.' "
Reference Muwatta Malik 507960
USC-MSA web (English) reference : Book 20, Hadith 94