From Sahih Bukhari (Hadith 860):
Narrated Anas bin Malik:My grandmother Mulaika invited Allah's Messenger (ﷺ) for a meal which she had prepared specially for him. He ate some of it and said, "Get up. I shall lead you in the prayer." I brought a mat that had become black owing to excessive use and I sprinkled water on it. Allah's Messenger (ﷺ) stood on it and prayed two rak`at; and the orphan was with me (in the first row), and the old lady stood behind us
Reference: Bukhari 860