وَعَنِ ابْنِ عُمَرَ
قَالَ: كَانَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يُصَلِّي فِي السَّفَرِ عَلَى رَاحِلَتِهِ حَيْثُ تَوَجَّهَتْ بِهِ يُومِئُ إِيمَاءً صَلَاةَ اللَّيْلِ إِلَّا الْفَرَائِضَ وَيُوتِرُ على رَاحِلَته
On a journey God’s Messenger would pray on his riding beast in whatever direction it turned, making a sign with his head* in prayer during the night, but not in the obligatory prayers; and he would observe a witr on his riding beast. *To indicate the bowing and the prostration.
Mishkat al-Masabih 1269, Book 5, Prayer, Hadith 747. 1 min read