It was narrated that Ibn 'Umar said:

"The Messenger of Allah ﷺ used to pray on his mount while on a journey, no matter what direction it was facing."
Malik said: "Abdullah bin Dinar said: 'And Ibn 'Umar used to do likewise.'"

أَخْبَرَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، عَنْ مَالِكٍ، عَنْ عَبْدِ اللَّهِ بْنِ دِينَارٍ، عَنِ ابْنِ عُمَرَ، قَالَ كَانَ رَسُولُ اللَّهِ ﷺ يُصَلِّي عَلَى رَاحِلَتِهِ فِي السَّفَرِ حَيْثُمَا تَوَجَّهَتْ بِهِ . قَالَ مَالِكٌ قَالَ عَبْدُ اللَّهِ بْنُ دِينَارٍ وَكَانَ ابْنُ عُمَرَ يَفْعَلُ ذَلِكَ .