Musannaf Ibn Abi Shaybah 5500 — The hour in which buying and selling

Burd said: I asked al-Zuhri: When do buying and selling become forbidden on Friday? He said: The adhan used to be given when the imam came out. Then Sayyiduna Uthman (may Allah be pleased with him) added a third adhan, after which the adhan began to be given at al-Zawra' (a place in the market of Madinah) to gather the people, so that the people would assemble. In my view, buying and selling should be abandoned at that time.