His grandmother Mulaykah invited the Messenger of Allah ﷺ to a meal she had prepared. He ate some of it, then said, "Get up so I may lead you in prayer."Anas said, "I went to a straw mat of ours that had turned black from long use, and I sprinkled it with water. The Messenger of Allah ﷺ stood on it, and I and the orphan stood behind him, with the elderly woman behind us. The Messenger of Allah ﷺ led us in two units of prayer and then left."
قال قرأت على عبد الرحمن: مالك عن إسحاق بن عبد الله بن أبي طلحة
أن جدته مليكة دعت رسول الله ﷺ لطعام صنعته فأكل منه ثم قال رسول الله ﷺ قوموا فلأصل لكم قال أنس فقمت إلى حصير لنا قد اسود من طول ما لبس فنضحته بماء فقام عليه رسول الله ﷺ فقمت أنا واليتيم وراءه والعجوز من ورائنا فصلى بنا رسول الله ﷺ ركعتين ثم انصرف
Its isnad is sahih, it was mentioned previously at 12269. As for his saying, "falousalli," in another version it is "falousalli" [with a shortened form], and both are grammatically valid, and the grammarians have discussion and citations concerning this.