Abu Hurayrah (radi Allahu anhu) reported that the Messenger of Allah (sal Allahu alaihi wa sallam) 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.”
[Sahih 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.”
The bond of brotherhood among the Muslims has been further strengthened by the list in this Hadith about the rights of Muslims on one another.
If all Muslims in a community uphold these rights of one another, then the bond between them will be unbreakable.
And Allah Knows Best!