The five rights of a Muslim on a Muslim
It is narrated in a Hadis, “The rights of a Muslim on a Muslim are five: (1) to return the greetings, (2) to visit the sick, (3) to follow the funeral processions, (4) to accept invitation, and (5) to reply the sneezer.
(Sahih Bukhari, vol. 1, pp. 421, Hadis 1240)