حَدَّثَنَا مُحَمَّدُ بْنُ جَعْفَرٍ حَدَّثَنَا شُعْبَةُ عَنْ خُبَيْبِ بْنِ عَبْدِ الرَّحْمَنِ عَنْ حَفْصِ بْنِ عَاصِمٍ عَنِ ابْنِ عُمَرَ أَنَّهُ كَانَ يُصَلِّي حَيْثُ تَوَجَّهَتْ بِهِ رَاحِلَتُهُ قَالَ وَكَانَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَفْعَلُهُ
مسند امام احمد بن حنبل · Hadith 5040
It was narrated from Ibn 'Umar that he used to pray in whatever direction his mount was facing, and he said: The Messenger of Allah (PBUH) used to do that.
Translated by Dr. Muhammad Muhsin Khan · Reviewed by Islamic University of Madinah · Published March 2020