Silsilat al-Ahadith al-Sahihah

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.”