Sahih al-Bukhari 430

Arabic

حَدَّثَنَا صَدَقَةُ بْنُ الْفَضْلِ، قَالَ أَخْبَرَنَا سُلَيْمَانُ بْنُ حَيَّانَ، قَالَ حَدَّثَنَا عُبَيْدُ اللَّهِ، عَنْ نَافِعٍ، قَالَ رَأَيْتُ ابْنَ عُمَرَ يُصَلِّي إِلَى بَعِيرِهِ وَقَالَ رَأَيْتُ النَّبِيَّ صلى الله عليه وسلم يَفْعَلُهُ‏.‏

English translation

Narrated Nafi`:"I saw Ibn `Umar praying while taking his camel as a Sutra in front of him and he said, "I saw the Prophet doing the same

Reference: Sahih al-Bukhari 430, Book of Prayers (Salat). English translation by Dr. Muhammad Muhsin Khan.