Abd al-Rahman bin Abi Layla said: Abu Musa al-Ash'ari (may Allah be pleased with him) came to visit al-Hasan bin Ali (may Allah be pleased with them both), and Ali (may Allah be pleased with him) said: "Have you come to visit the sick, or to gloat?" He said: "Rather, to visit the sick." Ali (may Allah be pleased with him) said: "If you have come to visit the sick, then I heard the Messenger of Allah (peace and blessings be upon him) say: 'When a man comes to visit his brother (in sickness), he walks among the fruit gardens of Paradise until he sits down. When he sits down, the mercy of Allah Almighty covers him. If he went in the morning, seventy thousand angels pray for his forgiveness until the evening; and if he goes at night, seventy thousand angels keep praying for his forgiveness until morning comes.'"
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6584