عَنْ عَامِرِ بْنِ رَبِيعَةَ رَضِيَ اللَّهُ عَنْهُ قَالَ: رَأَيْتُ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ يُسَبِّحُ وَهُوَ عَلَى الرَّاحِلَةِ وَيُوْمِئُ بِرَأْسِهِ قِبَلَ أَيِّ وَجْهٍ تَوَجَّهَ، وَلَمْ يَكُنْ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ يَصْنَعُ ذَلِكَ فِي الصَّلَاةِ الْمَكْتُوبَةِ
Sayyiduna Amir bin Rabi’ah (may Allah be pleased with him) says: I saw the Messenger of Allah (peace and blessings be upon him) performing voluntary prayers on his mount; he would gesture with his head (and did not mind) whichever direction he faced. However, the Messenger of Allah (peace and blessings be upon him) did not do so in obligatory prayers.