Anas said that when God’s Messenger was on a journey and wished to say voluntary prayers he made his she-camel face the <i>qibla</i> and said, “God is most great,” then prayed in whatever direction his mount made him face. Abu Dawud transmitted it.

وَعَنْ أَنَسٍ قَالَ: كَانَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ إِذَا سَافَرَ وَأَرَادَ أَنْ يَتَطَوَّعَ اسْتَقْبَلَ الْقِبْلَةَ بِنَاقَتِهِ فَكَبَّرَ ثُمَّ صَلَّى حَيْثُ وَجهه ركابه. رَوَاهُ أَبُو دَاوُد