The freed slave of Umm Uthman (may Allah be pleased with her) says that I heard Sayyiduna Ali (may Allah be pleased with him) say while he was on the pulpit: "When it is Friday, the devils go out to the markets with their banners; they hold people back with hindrances, remind them of their needs and keep them back from the Friday prayer. And early in the morning the angels go out with their banners to the doors of the mosque, and they write that such-and-such a man came at such-and-such an hour, and so-and-so came at such-and-such an hour. When a man sits in his place, listens attentively to the sermon and does not engage in idle talk, he has a double reward. When he sits in his place and is far away, remains silent and does not engage in idle talk, he has a single reward. And when a man stays in his place and listens attentively to the sermon as far as he can, but engages in idle talk and does not remain silent, he bears a double punishment, or he said: he bears a burden. And whoever says to his companion on Friday: Stop, has also engaged in idle talk, and whoever engages in idle talk has no Friday prayer." At the end of it is: I heard the Prophet (peace and blessings be upon him); he (peace and blessings be upon him) was saying this.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجمعة / 5834
Malik bin Abi Amir narrates from Uthman bin Affan (may Allah be pleased with him) that he used to say in his sermon, and he seldom left it out whenever he delivered a sermon: When the imam stands to deliver the sermon on Friday, listen attentively and remain silent, for the one who remains silent but cannot hear (the sermon) has a share (of reward) like that of the one who listens and remains silent. When the iqamah is called, straighten the rows and align your shoulders, for "straightening the rows is part of the completion of the prayer." Then he would not say the takbir until those who had been appointed to straighten the rows informed him that the rows had been straightened; when they informed him that the rows were straight, then he would begin the prayer.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجمعة / 5835
It is narrated from al-Hasan (may Allah have mercy on him) that he saw no harm in a person remembering Allah within himself (during the sermon) with takbir, tahlil and tasbih.
Mansur bin al-Mu'tamir (may Allah have mercy on him) asked Ibrahim (may Allah have mercy on him): Do you recite while the imam is delivering the sermon on Friday? He said: Perhaps it will not harm you.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجمعة / 5836