وَحَدَّثَنِي عُبَيْدُ اللَّهِ بْنُ عُمَرَ الْقَوَارِيرِيُّ، حَدَّثَنَا يَحْيَى بْنُ سَعِيدٍ، عَنْ عَبْدِ الْمَلِكِ بْنِ أَبِي سُلَيْمَانَ، قَالَ حَدَّثَنَا سَعِيدُ بْنُ جُبَيْرٍ، عَنِ ابْنِ عُمَرَ، قَالَ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم يُصَلِّي وَهُوَ مُقْبِلٌ مِنْ مَكَّةَ إِلَى الْمَدِينَةِ عَلَى رَاحِلَتِهِ حَيْثُ كَانَ وَجْهُهُ - قَالَ - وَفِيهِ نَزَلَتْ ‏[quran sura="2" aya_start="115" aya_end="115"]{‏ فَأَيْنَمَا تُوَلُّوا فَثَمَّ وَجْهُ اللَّهِ‏}‏

باب جَوَازِ صَلاَةِ النَّافِلَةِ عَلَى الدَّابَّةِ فِي السَّفَرِ حَيْثُ تَوَجَّهَتْ ‏‏

Ibn 'Umar reported that the Messenger of Allah (ﷺ) used to say prayer on his camel while coming from Mecca to Medina, in whatever direction his face had turned; and its was (in this context) that this verse was revealed:" So whether you turn thither is Allah's face" (ii. 115).

It is permissible to offer voluntary prayers atop one’s mount when travelling, no matter what direction it is facing

Sahih Muslim

وَحَدَّثَنَاهُ أَبُو كُرَيْبٍ، أَخْبَرَنَا ابْنُ الْمُبَارَكِ، وَابْنُ أَبِي زَائِدَةَ، ح وَحَدَّثَنَا ابْنُ نُمَيْرٍ، حَدَّثَنَا أَبِي كُلُّهُمْ، عَنْ عَبْدِ الْمَلِكِ، بِهَذَا الإِسْنَادِ نَحْوَهُ ‏.‏ وَفِي حَدِيثِ ابْنِ مُبَارَكٍ وَابْنِ أَبِي زَائِدَةَ ثُمَّ تَلاَ ابْنُ عُمَرَ [quran sura="2" aya_start="115" aya_end="115"]‏{‏ فَأَيْنَمَا تُوَلُّوا فَثَمَّ وَجْهُ اللَّهِ‏}‏ وَقَالَ فِي هَذَا نَزَلَتْ ‏.‏

This hadith has been narrated by another chain of transmitters and in the one narrated by Ibn Mubarak and Ibn Abu Za'ida (these words are narrated). Ibn 'Umar then recited:" Whether you turn thither is Allah's face," and it was revealed in this context.