The Messenger of Allah ﷺ said, "The one who sneezes is to be blessed three times. If he sneezes more than that, you may bless him if you wish, or you may leave it."
حدثنا القاسم بن دينار الكوفي حدثنا إسحق بن منصور السلولي الكوفي عن عبد السلام بن حرب عن يزيد بن عبد الرحمن أبي خالد عن عمر بن إسحق بن أبي طلحة
قال رسول الله ﷺ يشمت العاطس ثلاثا فإن زاد فإن شئت فشمته وإن شئت فلا
[Its chain is daif] Abu Dawud also narrated it in the book of Manners, chapter on who should say "may Allah have mercy on you" to one who sneezes, no. 5036, through the hadith of Abdul-Salam.Abu Khalid narrated with "an" (indicating a possible break in the chain), and the mother of Umar bin Ishaq, Humaydah or Ubayda, was not deemed reliable by anyone except Ibn Hibban, so her status is unknown.