Riyad as-Salihin, Book 1, Hadith 238 (In-Book) ⓘ

Abu Hurairah (May Allah bepleased with him) reported: Messenger of Allah said, "A believer owes another believer five rights: responding to greetings, visiting him in illness, following his funeral, accepting his invitation, and saying 'Yarhamuk-Allah (May Allah have mercy on you),' when he says 'Al-hamdu lillah (Praise be to Allah)' after sneezing".[Al-Bukhari and Muslim].Muslim's narration is, "There are six rights of a Muslim upon a Muslim: When you meet him, greet him; when he invites you, respond to him; when he seeks counsel, give him advice; when he sneezes and praises Allah, say to him: 'May Allah have mercy on you (Yarhamuk-Allah)'; when he is sick, visit him; and when he dies, follow his funeral".

وعن أبي هريرة رضي الله عنه أن رسول الله صلى الله عليه وسلم قال‏:‏ ‏ "‏حق المسلم على المسلم خمس‏:‏ رد السلام، وعيادة المريض، واتباع الجنائز وإجابة الدعوة، وتشميت العاطس‏" ‏ ‏(‏‏(‏متفق عليه‏)‏‏)‏ ‏.‏