Musnad Ahmad 5:600

Abdullah narrated to us, Muhammad ibn Abi Bakr al-Muqaddami narrated to me, Sa’id ibn Salamah—meaning Ibn Abi al-Husam—narrated to us, Muslim ibn Abi Maryam narrated to us, from a man of the Ansar, from Ali: That the Prophet, peace and blessings of Allah be upon him, said: "Whoever visits a sick person walks among the harvested fruits of Paradise. When he sits with him, he is submerged in mercy. When he leaves from him, seventy thousand angels are appointed to him, seeking forgiveness for him for that day."