Sunan Abu Dawud
Prayer (Kitab Al-Salat): Detailed Rules of Law about the Prayer during Journey
Hadith #30
4.30
حَدَّثَنَا عُثْمَانُ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا وَكِيعٌ، عَنْ سُفْيَانَ، عَنْ أَبِي الزُّبَيْرِ، عَنْ جَابِرٍ، - قَالَ - بَعَثَنِي رَسُولُ اللَّهِ صلى الله عليه وسلم فِي حَاجَةٍ قَالَ فَجِئْتُ وَهُوَ يُصَلِّي عَلَى رَاحِلَتِهِ نَحْوَ الْمَشْرِقِ وَالسُّجُودُ أَخْفَضُ مِنَ الرُّكُوعِ .
Narrated Jabir ibn Abdullah: The Messenger of Allah (ﷺ) sent me on some business, and when I came to him he was praying on (the back of) his riding beast (moving) towards the east and making the prostration lower than the bowing