The Muslim owes his fellow Muslim six (things): when you meet him, greet him; when he invites you, accept his invitation; when he asks for your advice, give him advice; when he sneezes and praises Allah, say: May Allah have mercy on you; when he is ill, visit him; and when he dies, follow his funeral. [Muslim]

حقُّ المسلم على المسلم ست: إذا لَقِيتَهُ فسَلِّمْ عليه, وإذا دعاك فَأَجِبْهُ، وإذا اسْتَنْصَحَكَ فانْصَحْهُ, وإذا عَطَسَ فَحَمِدَ الله فسَمِّتْهُ، وإذا مرض فعُدْهُ, وإذا مات فاتَّبِعْهُ» [صحيح.] - [رواه مسلم.]