“The Muslim has four things due from the Muslim: He should answer [by saying Yarhamuk-Allah (may Allah have mercy on you)] to him if he sneezes (and says Al-Hamdulillah); he should accept his invitation if he invites him; he should attend his funeral if he dies; and he should visit him if he falls sick.” (Using translation from Ibn Mājah 1434)
عَنِ النَّبِيِّ ﷺ قَالَ لِلْمُسْلِمِ عَلَى الْمُسْلِمِ أَرْبَعُ خِلَالٍ يُجِيبُهُ إِذَا دَعَاهُ وَيَعُودُهُ إِذَا مَرِضَ وَيُشَمِّتُهُ إِذَا عَطَسَ وَيُشَيِّعُهُ إِذَا مَاتَ