Musnad Ahmad 32:974

Bahz narrated to us, Shu'bah narrated to us, Anas ibn Sirin informed us, he said: I heard Anas ibn Malik say: There was a man from the Ansar who was large, and he could not pray with the Prophet, may Allah bless him and grant him peace. So he said to the Prophet, may Allah bless him and grant him peace: "I cannot pray with you." So he prepared food for him and invited the Prophet, may Allah bless him and grant him peace. They spread a mat for him and sprinkled it with water, and he prayed two rak'ahs upon it. A man from the family of Al-Jarud said to him: "Did the Messenger of Allah, may Allah bless him and grant him peace, pray the Duha (forenoon) prayer?" He said: "I did not see him pray it except on that day."