It is narrated from Hazrat Abu Huraira (may Allah be pleased with him) that he heard the Noble Prophet (peace and blessings be upon him) saying: When the Imam is delivering the Friday sermon and you say to your companion, "Be quiet," then you have engaged in idle talk.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 7686
Hadith Gradingحکم دارالسلام:هذا الحديث له إسنادان، وهما صحيحان، خ: 934، م: 851.