حَدَّثَنَا عَبْد اللَّهِ قَالَ وَجَدْتُ فِي كِتَابِ أَبِي حَدَّثَنَا يَزِيدُ أَخْبَرَنَا شُعْبَةُ عَنْ عَبْدِ اللَّهِ بْنِ دِينَارٍ عَنِ ابْنِ عُمَرَ أَنَّهُ كَانَ يُصَلِّي عَلَى رَاحِلَتِهِ حَيْثُ وَجَّهَتْ وَزَعَمَ أَنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ كَانَ يَفْعَلُهُ
مسند امام احمد بن حنبل · Hadith 5062
It was narrated from Ibn 'Umar that he used to pray (naafil) atop his mount no matter what direction it was facing, and he said that the Messenger of Allah (PBUH) used to do that.
Translated by Dr. Muhammad Muhsin Khan · Reviewed by Islamic University of Madinah · Published March 2020