Right of believers towards each other
It was reported from Abu Hurayrah (may Allah be pleased with him) that the Prophet SAW said: “If any one of you sneezes, let him say ‘Al-hamdu Lillaah,’ and let his brother or his companion say, ‘Yarhamuk Allah.’ And if he says to him, ‘Yarhamuk Allah,’ let him say, ‘Yahdeekum Allahu wa yusliha baalakum (May Allah guide you and correct your thinking).’” [Reported by al-Bukhari, 10/502]
This is actually a right our brothers and sisters have over us, we must reply back with Yarhamuk Allah if we hear someone say alhamdulillah after they sneeze, at least one of us must. This is a right they have over you much like giving Salam- you must reply to Salam (unless you are female, you don’t have to reply to a male if you fear it will lead to other things).
Getting to my point, ever wonder why we do this, besides the Prophet SAW’s order mentioned in the hadith above? Well, it dates all the way back to our Father Adam A.S. and when he was first brought to life by Allah SWT.
Allah’s Messenger (peace and blessings of Allah be upon him) said: ‘When Allah created Adam and breathed the spirit into him, he (Adam AS) sneezed and said, “Al-hamdu Lillaah (Praise be to Allah).” So he praised Allah by His permission and his Lord said to him, “Yarhamuk Allah (May Allah have mercy on you), Adam.” [Al-Tirmidhi Hadith 4662]
Adam’s (man’s) first word’s was Alhamdulillah to Allah and Allah’s first words to man was “May Allah have mercy on you.” Subhanallah, Allah forgiving Adam AS before he and any of mankind even made a mistake. How Merciful and Great is Allah SWT?