al-Bukhari added:

"Making gestures with his head and he did not do that (pray while mounted) with obligatory prayers."

زَادَ اَلْبُخَارِيُّ : { يُومِئُ بِرَأْسِهِ , وَلَمْ يَكُنْ يَصْنَعُهُ فِي اَلْمَكْتُوبَةِ } [1]‏ .‏