The Book of Prayer
Bulugh al-Maram #254
كتاب الصلاة
زَادَ اَلْبُخَارِيُّ: «يُومِئُ بِرَأْسِهِ, وَلَمْ يَكُنْ يَصْنَعُهُ فِي اَلْمَكْتُوبَةِ»
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"
"Making gestures with his head and he did not do that (pray while mounted) with obligatory prayers."
— Bulugh al-Maram, Hadith 254