Musnad Ahmad 30:2083

'Ali ibn Ishaq narrated to us, 'Abdullah informed us, he said: Al-Ajalih informed us, that Abu Burdah ibn Abi Musa al-Ash'ari informed him, from Abu Hurairah, he said: I heard the Messenger of Allah, peace and blessings of Allah be upon him, saying: "Indeed, there is an hour in Friday; no believing servant prays to Allah for anything during it, except that Allah answers him."