Sayyidma Anas (RA) ibn Malik reported that two men sneezed in the presense of the Prophet (SAW) who said: ‘yarhamakAllah’ to one of them but not to the other. So this man asked, “You prayed for him but not for me, O Messenger of Allah (SAW).” He said, “He had praised Allah, but you did not.”
[Ahmed 11962, Bukhari 6221, Muslim 2991,Abu Dawud 5039, Ibn e Majah 3713]