The grandmother of Sayyiduna Anas bin Malik (may Allah be pleased with him) invited the Messenger of Allah (peace and blessings be upon him) to a meal. He (peace and blessings be upon him) ate, then said: "Stand up, so that I may lead you in prayer." Sayyiduna Anas (may Allah be pleased with him) says: I went to a mat of ours that had turned black from long use. I sprinkled it with water, and the Messenger of Allah (peace and blessings be upon him) stood on it. A boy and I formed a row behind him (peace and blessings be upon him), and the old woman was behind us. Then he (peace and blessings be upon him) led us in two rak'ahs of prayer, and then he left.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 5160