حَدَّثَنِي مَالِكٌ، عَنْ عَبْدِ اللَّهِ بْنِ أَبِي بَكْرٍ، عَنْ أَبِيهِ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏"‏ إِنْ عَطَسَ فَشَمِّتْهُ ثُمَّ إِنْ عَطَسَ فَشَمِّتْهُ ثُمَّ إِنْ عَطَسَ فَشَمِّتْهُ ثُمَّ إِنْ عَطَسَ فَقُلْ إِنَّكَ مَضْنُوكٌ ‏"‏ ‏.‏ قَالَ عَبْدُ اللَّهِ بْنُ أَبِي بَكْرٍ لاَ أَدْرِي أَبَعْدَ الثَّالِثَةِ أَوِ الرَّابِعَةِ

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." Translation Not Available

Book reference: Muwatta Imam Malik Book 54 Hadith 1769
Web reference: Muwatta Imam Malik Book 54 Hadith 4