وعن أنس رضي الله عنه
قال: عطس رجلان عند النبي صلى الله عليه وسلم، فشمت أحدهما ولم يشمت الآخر، فقال الذي لم يشمته: عطس فلان فشمته، وعطست فلم تشمتني؟ فقال: «هذا حمد الله، وإنك لم تحمد الله»
When two men sneezed in the presence of the Prophet (sallallahu alayhi wa sallam), he responded to one with “Yarhamuk-Allah (may Allah have mercy on you)” and did not respond to the other. The latter said to him: “You invoked a blessing on this man but did not do so in my case.” The Prophet (sallallahu alayhi wa sallam) replied, “He praised Allah (i.e., he said ‘Al-hamdu lillah’) but you did not.”.
Riyad as-Salihin 881, Book 6, The Book of Greetings, Hadith 38. 1 min read