"The believer owes six duties toward his fellow believer: To visit him when he is sick, to attend his funeral when he dies, to accept his invitation, to greet him with Salam when he meets him, to reply to him (say: Yarhamuk Allah, may Allah have mercy on you) when he sneezes and to be sincere to him, whether he is absent or present." (Hasan).
أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ لِلْمُؤْمِنِ عَلَى الْمُؤْمِنِ سِتُّ خِصَالٍ يَعُودُهُ إِذَا مَرِضَ وَيَشْهَدُهُ إِذَا مَاتَ وَيُجِيبُهُ إِذَا دَعَاهُ وَيُسَلِّمُ عَلَيْهِ إِذَا لَقِيَهُ وَيُشَمِّتُهُ إِذَا عَطَسَ وَيَنْصَحُ لَهُ إِذَا غَابَ أَوْ شَهِدَ