حَدَّثَنَا هَنَّادُ بْنُ السَّرِيِّ، حَدَّثَنَا أَبُو الأَحْوَصِ، عَنْ أَبِي إِسْحَاقَ، عَنِ الْحَارِثِ، عَنْ عَلِيٍّ، قَالَ قَالَ رَسُولُ اللَّهِ ـ صلى الله عليه وسلم ـ ‏"‏ لِلْمُسْلِمِ عَلَى الْمُسْلِمِ سِتَّةٌ بِالْمَعْرُوفِ يُسَلِّمُ عَلَيْهِ إِذَا لَقِيَهُ وَيُجِيبُهُ إِذَا دَعَاهُ وَيُشَمِّتُهُ إِذَا عَطَسَ وَيَعُودُهُ إِذَا مَرِضَ وَيَتْبَعُ جِنَازَتَهُ إِذَا مَاتَ وَيُحِبُّ لَهُ مَا يُحِبُّ لِنَفْسِهِ ‏"‏ ‏.‏

It wasnarrated that ‘Ali said that the Messenger of Allah (PBUH)said: “The Muslim has six courtesies due from the Muslim: He shouldgreethim with Salam when he meets him; he should accept hisinvitation ifhe invites him; he should answer [by Yarhamuk-Allah (mayAllah havemercy on you)] to him if he sneezes (and says Al-Hamdulillah); heshould visit him if he falls sick; he should followhis funeral if hedies; and he should love for him what he loves forhimself.” Translation Not Available

Book Ref: Sunan Ibn Majah Book 6 Hadith 1433
Web Ref:  Sunan Ibn Majah Vol 1 Book 6 Hadith 1433