If you (even) ask your companion to be quiet on Friday while the Imam is delivering the sermon, you have in fact talked irrelevance.  

أَخْبَرَهُ أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ إِذَا قُلْتَ لِصَاحِبِكَ أَنْصِتْ يَوْمَ الْجُمُعَةِ وَالإِمَامُ يَخْطُبُ فَقَدْ لَغَوْتَ  

A hadith like this has been narrated by Abu Huraira by another chain of transmitters.  

سَمِعْتُ رَسُولَ اللَّهِ ﷺ يَقُولُ بِمِثْلِهِ  

"Ibrahim bin 'Abdullah bin Qariz."  

إِبْرَاهِيمُ بْنُ عَبْدِ اللَّهِ بْنِ قَارِظٍ  

The same hadith has been narrated by Abu Huraira, but instead of the word laghauta the word laghita has been used. Abu Zinad (one of the narrators) says that laghita is the dialect of Abu Huraira, whereas it is laghauta.  

عَنِ النَّبِيِّ ﷺ قَالَ إِذَا قُلْتَ لِصَاحِبِكَ أَنْصِتْ يَوْمَ الْجُمُعَةِ وَالإِمَامُ يَخْطُبُ فَقَدْ لَغِيتَ قَالَ أَبُو الزِّنَادِ هِيَ لُغَةُ أَبِي هُرَيْرَةَ وَإِنَّمَا هُوَ فَقَدْ لَغَوْتَ