Riyad as-Salihin, Book 6, Hadith 881 (In-Book) ⓘ

Anas (May Allah be pleased with him) reported: When two men sneezed in the presence of the Prophet, 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 replied, "He praised Allah (i.e., he said 'Al-hamdu lillah') but you did not."[Al-Bukhari and Muslim].

وعن أنس رضي الله عنه قال‏:‏ عطس رجلان عند النبي صلى الله عليه وسلمى الله عليه وسلم 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" ‏ ‏(‏‏(‏متفق عليه‏)‏‏)‏