Sahih al-Bukhari 1104

Arabic

وَقَالَ اللَّيْثُ حَدَّثَنِي يُونُسُ، عَنِ ابْنِ شِهَابٍ، قَالَ حَدَّثَنِي عَبْدُ اللَّهِ بْنُ عَامِرٍ، أَنَّ أَبَاهُ، أَخْبَرَهُ أَنَّهُ، رَأَى النَّبِيَّ صلى الله عليه وسلم صَلَّى السُّبْحَةَ بِاللَّيْلِ فِي السَّفَرِ عَلَى ظَهْرِ رَاحِلَتِهِ حَيْثُ تَوَجَّهَتْ بِهِ‏.‏

English translation

Narrated `Abdullah bin Amir that his father had told him that he had seen the Prophet (ﷺ) praying Nawafil at night on the back of his Mount on a journey, facing whatever direction it took

Reference: Sahih al-Bukhari 1104, Book of Shortening the Prayers (At-Taqseer). English translation by Dr. Muhammad Muhsin Khan.