Bulugh al-Maram 2 The Book of Prayer كتاب الصلاة 76

وَلِأَبِي دَاوُدَ : مِنْ حَدِيثِ أَنَسٍ : { كَانَ إِذَا سَافَرَ فَأَرَادَ أَنْ يَتَطَوَّعَ اِسْتَقْبَلَ بِنَاقَتِهِ اَلْقِبْلَةِ , فَكَبَّرَ , ثُمَّ صَلَّى حَيْثُ كَانَ وَجْهَ رِكَابِهِ } وَإِسْنَادُهُ حَسَنٌ . 1 1 – حسن . رواه أبو داود (1225) وصححه غير واحد .

Narrated Anas in another narration of the Hadith reported by Abu Dawud: When [he (صلى الله عليه وسلم)] traveled, and intended to pray a voluntary prayer, he used to direct his riding camel towards the Qiblah, say, “Allahu Akbar” and pray facing whatever direction it faced. [Its chain is Hasan (good)].