وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ عَبْدِ اللَّهِ بْنِ دِينَارٍ، عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم كَانَ يُصَلِّي عَلَى رَاحِلَتِهِ فِي السَّفَرِ حَيْثُ تَوَجَّهَتْ بِهِ ‏.‏ قَالَ عَبْدُ اللَّهِ بْنُ دِينَارٍ وَكَانَ عَبْدُ اللَّهِ بْنُ عُمَرَ يَفْعَلُ ذَلِكَ ‏.‏

Yahya related to me from Malik from Abdullah ibn Dinar fromAbdullah ibn Umar that the Messenger of Allah, may Allah bless him andgrant him peace, used to pray on his mount while travelling, whicheverway it was facing. Abdullah ibn Dinar said, "Abdullah ibn Umar wouldalso do that." Translation Not Available

Book Ref: Muwatta Imam Malik Book 9 Hadith 357
Web Ref:  Muwatta Imam Malik Book 9 Hadith 28