Hazrat Anas bin Malik (may Allah be pleased with him) narrates that two men sneezed in the presence of the Noble Prophet (peace and blessings be upon him). The Prophet (peace and blessings be upon him) supplicated "Yarhamukallah" (may Allah have mercy on you) for one of them, but did not say "Yarhamukallah" for the other. It was asked of the Prophet (peace and blessings be upon him): O Messenger of Allah (peace and blessings be upon him)! Two men sneezed in your presence. You supplicated "Yarhamukallah" for one of them, but did not say "Yarhamukallah" for the other? The Prophet (peace and blessings be upon him) replied: He said "Alhamdulillah" and the other did not say "Alhamdulillah."

Hazrat Abu Burdah narrates that I came to Hazrat Abu Musa while he was in the house of Bint Fazl. I sneezed, but he did not say "Yarhamukallah" to me, and when Bint Fazl sneezed, he said "Yarhamukallah" to her. I returned to my mother and informed her about this. When she came to him, she said: "Indeed, my son sneezed in your presence, but you did not say 'Yarhamukallah' to him, and this girl sneezed and you said 'Yarhamukallah' to her." He replied: "Your son sneezed but did not say 'Alhamdulillah', so I did not say 'Yarhamukallah' to him, and this girl sneezed and she said 'Alhamdulillah', so I responded to her with 'Yarhamukallah'. And I heard the Messenger of Allah (peace and blessings be upon him) say: When any of you sneezes and says 'Alhamdulillah', then you should pray for him by saying 'Yarhamukallah', and if he does not say 'Alhamdulillah', then you should not say 'Yarhamukallah' to him."

Hazrat Abu Huraira narrates that the Messenger of Allah, peace and blessings be upon him, said: A Muslim has a right over another Muslim: when someone sneezes and says "Alhamdulillah," he should respond by saying "Yarhamuk Allah" and pray for him.

Hazrat Abu Huraira narrates that we were sitting with the Noble Prophet (peace and blessings be upon him) when a man sneezed and said, "Alhamdulillah." The Noble Prophet (peace and blessings be upon him) said, "Yarhamukallah." Then another man sneezed, but the Prophet (peace and blessings be upon him) remained silent and did not say anything to him. That man said, "O Messenger of Allah (peace and blessings be upon him)! When he sneezed, you prayed for him by saying 'Yarhamukallah,' but when I sneezed, you did not pray for me!" The Prophet (peace and blessings be upon him) replied, "He said 'Alhamdulillah,' but you remained silent."

Hazrat Ghalib says that Hasan Basri and Hazrat Ibn Sirin, both of these personalities, would not say "Yarhamukallah" as a prayer for the one who sneezed until he said "Alhamdulillah."

Hazrat Ubaidullah narrates that a man sneezed in the presence of Hazrat Qasim, so Hazrat Qasim said to him: Say Alhamdulillah. When he said it, Hazrat Qasim prayed for him by saying Yarhamukallah.