OBLIGATIONS H 239 "There are five obligations owed by a Muslim to another: the return of his greeting, visiting him in sickness, attending his funeral, accepting his invitation, and saying: 'May Allah have mercy on you' after he has said: 'All praise is due to Allah' when he sneezed. In another narration: "There are six obligations owed by one Muslim to another. Upon meeting him he says: 'Peace be upon you.' When he invites you accept the invitation. When he asks your advice you advise him, When he sneezes and praises Allah, say to him: 'May Allah have mercy on you.' When he is sick you visit him. When he dies you attend his funeral." R 239 Bukhari and Muslim with a chain up to Abu Hurairah who related that the Prophet, praise and peace be upon him, said this.
238- وعن أَبي هريرة رضي الله عنه : أنَّ رَسُول الله صلى الله عليه وآله وسلم ، قَالَ : "حَقُّ المُسْلِم عَلَى المُسْلِم خَمْسٌ : رَدُّ السَّلامِ ، وَعِيَادَةُ المَريض ، وَاتِّبَاعُ الجَنَائِزِ ، وَإجَابَةُ الدَّعْوَة ، وتَشْميتُ العَاطِسِ" مُتَّفَقٌ عَلَيهِ . وفي رواية لمسلم : "حَقُّ المُسْلِم عَلَى المُسْلِم ستٌّ : إِذَا لَقيتَهُ فَسَلِّمْ عَلَيهِ ، وَإِذَا دَعَاكَ فَأجبْهُ ، وإِذَا اسْتَنْصَحَكَ فَانْصَحْ لَهُ ، وإِذَا عَطَسَ فَحَمِدَ الله فَشَمِّتْهُ ، وَإِذَا مَرِضَ فَعُدْهُ ، وَإِذَا مَاتَ فَاتَّبِعْهُ" .