It was narrated from Abu Hurairah that:
The Messenger of Allah (ﷺ) said: "Whoever says to his companion on Friday, when the imam is delivering the khutbah: 'Listen attentively,' has engaged in idle talk." (ES)
App reference (ES): Book 14, Hadith 38 (ES)
English reference (ES): Vol. 2, Book 14, Hadith 1402 (ES)
Arabic reference (ES): Book 14, Hadith 1412 (ES)