"I asked whether the Messenger of Allah prayed voluntary prayer when traveling, but I could not find anyone to tell me until Umm Hani' bint Abu Talib told me that he had come during the year of the Conquest (of Makkah). He ordered that a screen be held up, and that was done, and he took a bath; then he prayed eight Rak'ah (units) of voluntary prayer." (Using translation from Ibn Mājah 614)
أَنَّ رَسُولَ اللهِ ﷺ سَبَّحَ فِي سَفَرِهِ فَلَمْ أَجِدْ أَحَدًا يُخْبِرُنِي عَنْ ذَلِكَ حَتَّى أَخْبَرَتْنِي أُمُّ هَانِئٍ بِنْتُ أَبِي طَالِبٍ أَنَّهُ قَدِمَ عَامَ الْفَتْحِ فَأَمَرَ بِسِتْرٍ فَسُتِرَ عَلَيْهِ ثُمَّ سَبَّحَ ثَمَانِ رَكَعَاتٍ خَالَفَهُ الزُّبَيْدِيُّ