Yahya related to me from Malik from Nafi that Abdullah ibn Umarused to pray in the mosque of Dhu'l-Hulayfa, and then go outside andget on his camel and when his camel had stood up he would begin to dotalbiya. (ES)
USC-MSA web (English) reference: Book 20, Hadith 32 (ES)
Arabic reference (ES): Book 20, Hadith 740 (ES)