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."