Hadith 507370
Chapter 20: Hajj - كتاب الحج
وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ هِشَامِ بْنِ عُرْوَةَ، عَنْ أَبِيهِ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم كَانَ يُصَلِّي فِي مَسْجِدِ ذِي الْحُلَيْفَةِ رَكْعَتَيْنِ فَإِذَا اسْتَوَتْ بِهِ رَاحِلَتُهُ أَهَلَّ .
Yahya related to me from Malik from Hisham ibn Urwa from his father that the Messenger of Allah, may Allah bless him and grant him peace, used to pray two rakas in the mosque at Dhu'l-Hulayfa, and then, when he had got on to his camel and it had stood up, he would begin doing talbiya.
Reference Muwatta Malik 507370
USC-MSA web (English) reference : Book 20, Hadith 29