(48) باب جَوَازِ الْجَمَاعَةِ فِي النَّافِلَةِ وَالصَّلاَةِ عَلَى حَصِيرٍ وَخُمْرَةٍ وَثَوْبٍ وَغَيْرِهَا مِنَ الطَّاهِرَاتِ
Abu Sa'id al-Khudri reported that he went to the Messenger of Allah (ﷺ) and found him observing prayer on a mat and prostrating on that. (ID)
Reference (ID): Sahih Muslim 661 (ID)
In-book reference (ID): Book 5, Hadith 341 (ID)
USC-MSA web (English) reference(deprecated numbering scheme): Book 4, Hadith 1393 (ID)