Musnad Ahmad 5:412

Muhammad ibn Ja'far narrated to us, Shu'bah narrated to us, from al-Hakam, from Abdullah ibn Nafi', who said: Abu Musa al-Ash'ari visited al-Hasan ibn Ali ibn Abi Talib, so Ali said to him: "Have you come as a visitor of the sick (a'idan) or as a visitor (za'iran)?" He said: "No, rather I have come as a visitor of the sick." Ali said: "As for that, there is no Muslim who visits a sick person except that seventy thousand angels go out with him, all of them seeking forgiveness for him. If he is in the morning, they do so until the evening, and he will have a harvested portion in Paradise. And if he is in the evening, seventy thousand angels go out with him, all of them seeking forgiveness for him until he reaches the morning, and he will have a harvested portion in Paradise."