Silsilat al-Ahadith al-Sahihah

It is narrated from Sayyiduna Abu Hurairah (may Allah be pleased with him) that the Noble Prophet (peace and blessings of Allah be upon him) said: "These three rights are obligatory upon every Muslim: to visit the sick, to attend funerals, and when someone who sneezes says « «اَلْحَمْدُ لِلّٰهِ», to say to him «يرحمك الله» 'May Allah have mercy on you.'"