" للمؤمن على المؤمن ست خصال: يعوده إذا مرض ويشهده إذا مات ويجبيه إذا دعاه ويسلم عليه إذا لقيه ويشمته إذا عطس وينصح له إذا غاب أو شهد "
The Prophet (peace and blessings be upon him) said:
"The believer has six rights over the believer: to visit him when he is ill, to attend his funeral when he dies, to accept his invitation when he invites him, to greet him with salam when he meets him, to say 'Yarhamuk Allah' (May Allah have mercy on you) when he sneezes, and to be sincere towards him both in his absence and in his presence."
Hadith Referenceصحیح الجامع الصغیر / حرف اللام / 5188