Musnad Ahmad 5:411

'Abdullah ibn Yazid 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. 'Ali said to him: "Have you come as one visiting a sick person (a'idan) or as a visitor (za'iran)?" Abu Musa said: "Rather, I have come as one visiting a sick person." 'Ali said: "I heard the Messenger of Allah, peace and blessings of Allah be upon him, say: 'Whoever visits a sick person in the morning, seventy thousand angels accompany him, all of them asking for forgiveness for him until he reaches the evening, and he will have a garden in Paradise. And if he visits him in the evening, seventy thousand angels accompany him, all of them asking for forgiveness for him until he reaches the morning, and he will have a garden in Paradise.'"