Sahih Muslim Book 4, Hadith Number 2011.

Chapter : Visiting the sick.

‘Abdullah b. ‘Umar reported: While we were sitting with the Messenger of Allah (may peace be upon him), a person, one of the Ansar, came to him and greeted him. The Ansari then turned back. Upon this the Messenger of Allah (may peace be upon him) said: o brother of Ansar, how is my brother Sa’d be ‘Ubada? He said: He is better. The Messenger of Allah (may peace be upon him) said: Who amongst you would visit him? He (the Holy Prophet) stood up and we also got up along with him, and we were more than ten persons. We had neither shoes with us, nor socks, nor caps, nor shirts. We walked on the barren land till we came to him. The people around him kept away till the Messenger of Allah (may peace be upon him) and his Companions with him came near him (Sa’d b. ‘Ubada).