Ibn 'Abbas narrated:
"'Umar bin Al-Khattab informed me, saying: 'I entered upon the Messenger of Allah (s.a.w) and saw him reclining upon a mat woven from fibers, and I could see the impressions it left upon his side.'" (DE)
English reference (DE): Vol. 4, Book 11, Hadith 2461 (DE)
Arabic reference (DE): Book 37, Hadith 2649 (DE)