Musnad Abu Ya'la al-Mawsili 160:233

And with his chain of narration from Abu Hurayrah, he said: Two men sat with the Messenger of Allah, may Allah bless him and grant him peace, one of them being more noble than the other. The noble one among them sneezed, but he did not praise Allah, so he did not say "Yarhamuk Allah" (may Allah have mercy on you) to him. Then the other sneezed and praised Allah, so he said "Yarhamuk Allah" to him.