Authentic
graded by Salim al-Hilali
Muwatta Malik 235
وَحَدَّثَنِي عَنْ مَالِكٍ، أَنَّهُ بَلَغَهُ أَنَّ رَجُلاً، عَطَسَ يَوْمَ الْجُمُعَةِ وَالإِمَامُ يَخْطُبُ فَشَمَّتَهُ إِنْسَانٌ إِلَى جَنْبِهِ فَسَأَلَ عَنْ ذَلِكَ سَعِيدَ بْنَ الْمُسَيَّبِ فَنَهَاهُ عَنْ ذَلِكَ وَقَالَ لاَ تَعُدْ .
Yahya related to me from Malik that he had heard that a man sneezed on the day of jumua while the imam was giving the khutba, and a man by his side asked Allah to bless him. Said ibn al Musayyab was asked about it and he forbade the man to do what he had done and said, "Don't do it again."
Reported by Malik (No. 235).