Anas reported that his grandmother Mulaykah invited the Messenger of Allah ﷺ to a meal she had prepared for him. He ate some of it, then said, "Get up so I may lead you in prayer."Anas said, "I went to a mat of ours that had turned black from long use and sprinkled it with water. The Messenger of Allah ﷺ stood, and I and the orphan boy lined up behind him, with the old woman behind us. He led us in two units of prayer, then departed."
أخبرنا قتيبة بن سعيد عن مالك عن إسحق بن عبد الله بن أبي طلحة
أن جدته مليكة دعت رسول الله ﷺ لطعام قد صنعته له فأكل منه ثم قال قوموا فلأصلي لكم قال أنس فقمت إلى حصير لنا قد اسود من طول ما لبس فنضحته بماء فقام رسول الله ﷺ وصففت أنا واليتيم وراءه والعجوز من ورائنا فصلى لنا ركعتين ثم انصرف
Bukhari transmitted it in the Book of Prayer, chapter on praying on a mat, hadith 380, and Muslim in the Book of Mosques and so on, hadith 658, from the hadith of Malik through this same chain. It is also found in the Muwatta, chapter on the permissibility of congregational prayer in optional prayers (Yahya's version): 1/153, and in the Kubra, hadith 876.