Yahya related to me from Malik from Nafi that Abdullah ibn Umar saw two men talking while the imam was giving the khutba on the day of jumua and he threw pebbles at them to tell them to be quiet.
أَنَّ عَبْدَ اللَّهِ بْنَ عُمَرَ رَأَى رَجُلَيْنِ يَتَحَدَّثَانِ وَالإِمَامُ يَخْطُبُ يَوْمَ الْجُمُعَةِ فَحَصَبَهُمَا أَنِ اصْمُتَا
Yahya related to me from Malik that he had heard that Umar ibn al-Khattab had sent (the following message) to al-Harith ibn Hisham, ''Tomorrow is the day of Ashura, so fast (it) and tell your family to fast (also)."
أَنَّهُ بَلَغَهُ أَنَّ عُمَرَ بْنَ الْخَطَّابِ أَرْسَلَ إِلَى الْحَارِثِ بْنِ هِشَامٍ أَنَّ غَدًا يَوْمُ عَاشُورَاءَ فَصُمْ وَأْمُرْ أَهْلَكَ أَنْ يَصُومُوا
"مَنْ صَمَتَ نَجَا".