"'Umar bin Al-Khattab informed me, saying: 'I entered upon the Messenger of Allah ﷺ and saw him reclining upon a mat woven from fibers, and I could see the impressions it left upon his side.'"  

دَخَلْتُ عَلَى رَسُولِ اللَّهِ ﷺ فَإِذَا هُوَ مُتَّكِئٌ عَلَى رَمْلِ حَصِيرٍ فَرَأَيْتُ أَثَرَهُ فِي جَنْبِهِ