Hadith 4470

(حديث مرفوع) حَدَّثَنَا مُعْتَمِرُ بْنُ سُلَيْمَانَ ، عَنْ عُبَيْدِ اللَّهِ ، عَنْ نَافِعٍ ، قَالَ : رَأَيْتُ ابْنَ عُمَرَ " يُصَلِّي عَلَى دَابَّتِهِ التَّطَوُّعَ حَيْثُ تَوَجَّهَتْ بِهِ ، فَذَكَرْتُ لَهُ ذَلِكَ ، فَقَالَ : رَأَيْتُ أَبَا الْقَاسِمِ يَفْعَلُهُ .
Nafi' (may Allah have mercy on him) says: I saw Sayyiduna Ibn Umar (may Allah be pleased with them both) performing voluntary prayers on his mount, regardless of which direction it was facing. I once asked him about this, so he said: I saw Abu al-Qasim (peace and blessings of Allah be upon him) doing the same.
Hadith Reference مسند احمد / مسند المكثرين من الصحابة / 4470
Hadith Grading حکم دارالسلام: إسناده صحيح، خ: 1000، م: 700