Fiqh-us-Sunnah Volume 4, Funerals and Dhikr, Fiqh 4.003.

It is Islamic etiquette to visit a sick Muslim, to provide him moral support, and to make sure that he or she is well taken care of.

Ibn ‘Abbas said: “The first visit to a sick person is sunnah, while any subsequent visit is a voluntary act (a good deed).” Abu Musa reported that the Prophet, peace be upon him, said: “Feed the hungry, visit the sick, and free the captives.”

The Prophet, peace be upon him, said: “A Muslim has six obligations to another Muslim.” “What are these?” they asked. He replied: “To greet another Muslim when you meet him; to respond when he invites you; to give him your (sincerest) advice when he seeks it; to say ‘may Allah have mercy upon you’ when he sneezes and says ‘may Allah be praised ‘; to visit him when he falls ill; and when he dies, to attend his funeral.”