Sayyiduna Anas (may Allah be pleased with him) said that the Prophet (peace and blessings be upon him) came to the house of Sayyidah Umm Haram (may Allah be pleased with her), and she offered ghee and dates. He (peace and blessings be upon him) said: "Put this back in its container and this in its waterskin; I am fasting." Then he (peace and blessings be upon him) prayed two voluntary rak'ahs. Sayyidah Umm Sulaym and Sayyidah Umm Haram (may Allah be pleased with them both) stood behind us. Thabit (may Allah have mercy on him) said: As far as I know, he said: Then he (peace and blessings be upon him) made me stand on his right, and then he led us in prayer on the mat as an expression of gratitude.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4281