It is narrated from Anas bin Malik (may Allah be pleased with him) that his grandmother, Malikah (may Allah be pleased with her), invited the Messenger of Allah (ﷺ) for a meal which she had prepared as a hospitality for him. The Prophet (ﷺ) ate the food, then said: "Come, let me lead you in prayer." Anas bin Malik (may Allah be pleased with him) said: We stood on a mat which had turned black due to its oldness. I cleaned it with water, then the Messenger of Allah (ﷺ) stood on it, and I and the orphan (Dhumairah bin Sa'd) formed a row behind him, and (my) elderly (grandmother) was behind us.
Hadith Referenceمسند الإمام الشافعي / كتاب الصلاة / 285
Hadith Takhrijاخرجہ البخاری، الصلاة، باب الصلاة علی الحصیر: 380، ومسلم، المساجد، باب جواز الجماعة فی النافلة، والصلاة علی حصیر وخمرة وثوب وغیرہا من الطاہرات: 658۔