Sunan Abi Dawud 21090
In-book no 586حَدَّثَنَا النُّفَيْلِيُّ، حَدَّثَنَا زُهَيْرٌ، حَدَّثَنَا عَاصِمٌ الأَحْوَلُ، عَنْ عَمْرِو بْنِ سَلِمَةَ، بِهَذَا الْخَبَرِ قَالَ فَكُنْتُ أَؤُمُّهُمْ فِي بُرْدَةٍ مُوصَلَةٍ فِيهَا فَتْقٌ فَكُنْتُ إِذَا سَجَدْتُ خَرَجَتِ اسْتِي .
This tradition has also been transmitted through a different chain by ‘Amr b. Salamah. This version says: “I used to lead them in prayer with a sheet of cloth on me that was patched and torn. When I prostrated myself, my buttocks were disclosed.