Sahih Muslim Book 45, Hadith 48
This hadith has been narrated on the authority of Hammid b. Salama with the same of transmitters.
A person visited his brother in another town and Allah deputed an Angel to wait for him on his way and when he came to him he said: Where do you intend to go? He said: I intend to go to my brother in this town. He said: Have you done any favour to him (the repayment of which you intend to get)? He said: No, excepting this that I love Mm for the sake of Allah, the Exalted and Glorious. Thereupon he said: I am a meesenger to you from, Allah: (to inform you) that Allah loves you as you love him (for His sake).
The one who visits the sick is in fact like one who is in the fruit garden of Paradise so long as he does not return.