Malik related to me from Abdullah ibn Abi Bakr from his fatherthat the Messenger of Allah, may Allah bless him and grant him peace,said, "If a man sneezes, invoke a blessing on him. Then if he sneezes,invoke a blessing on him. Then if he sneezes, invoke a blessing onhim. Then if he sneezes, say, 'You have a cold'." Abdullah ibn AbiBakr said, "I don't know whether it was after the third or fourth."
USC-MSA web (English) reference: Book 54, Hadith 4
Arabic reference: Book 54, Hadith 1769