Silsilat al-Ahadith al-Sahihah

It is narrated from Sayyiduna Abu Hurairah, may Allah be pleased with him, who says that the Messenger of Allah, peace and blessings be upon him, said: “A Muslim has five rights over another Muslim: returning the greeting of peace, accepting an invitation, following funeral processions, visiting the sick, and responding to the sneeze of one who sneezes, provided he says «اَلْحَمْدُ لِلّٰهِ».”

It is narrated from Sayyiduna Abu Mas’ud (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him) said: “A Muslim has four rights over another Muslim: When he sneezes and ( «اَلْحَمْدُ لِلّٰهِ» says ) then he should be replied with «يرحمك الله» ‘May Allah have mercy on you’; when he invites, his invitation should be accepted; when he dies, his funeral should be attended; and when he falls ill, he should be visited.”