Musnad Ahmad 31:357

Mu'awiyah narrated to us, Shayban narrated to us, from Firas, from 'Atiyyah, from Abu Sa'id, from the Prophet of Allah, peace be upon him, who said: "If a man purifies himself and performs the purification well, then comes to the Friday prayer and does not engage in idle talk, and does not act ignorantly until the Imam finishes, it will be an expiation for what is between it and the [next] Friday. And in Friday, there is an hour; no believing man coincides with it while asking Allah for something, but He will give it to him. And the prescribed prayers are expiations for what is between them."