Hadith 146:24
Hajjaj narrated to us, Laith narrated to us, Aqil narrated to me, from Ibn Shihab, from Abdullah ibn Amir ibn Rabi'ah, that Amir ibn Rabi'ah said: "I saw the Messenger of Allah, may Allah bless him and grant him peace, performing voluntary prayer (tasbih) while he was on his riding beast, and he would gesture with his head in whichever direction it faced. And the Messenger of Allah, may Allah bless him and grant him peace, would not do that in the obligatory prayer."
حدثنا حجاج، حدثنا ليث، حدثني عقيل، عن ابن شهاب، عن عبد الله بن عامر بن ربيعة، أن عامر بن ربيعة، قال: " رأيت رسول الله صلى الله عليه وسلم يسبح وهو على الراحلة، ويومئ برأسه قبل أي وجه توجه، ولم يكن رسول الله صلى الله عليه وسلم يصنع ذلك في الصلاة المكتوبة "