It wasnarrated from Abu Hurairah that the Messenger of Allah (ﷺ)said:
"Five are the rights of the Muslim: Returning his greeting,accepting his invitation; attending his funeral; visiting the sick;and answering (saying Yarhamuk-Allah) to the one who sneezes, if hepraises Allah (says Al-Hamdu Lillah)." (FR)
English reference (FR): Vol. 1, Book 6, Hadith 1435 (FR)
Arabic reference (FR): Book 6, Hadith 1502 (FR)