Sahih Bukhari Volume 1, Book 11, Hadith Number 639

Narated By Anas bin Sirin : I heard Anas saying, “A man from Ansar said to the Prophet, ‘I cannot pray with you (in congregation).’ He was a very fat man and he prepared a meal for the Prophet and invited him to his house. He spread out a mat for the Prophet, and washed one of its sides with water, and the Prophet prayed two Rakat on it.” A man from the family of Al-Jaruid asked, “Did the Prophet used to pray the Duha (forenoon) prayer?” Anas said, “I did not see him praying the Duha prayer except on that day.”