Musannaf Ibn Abi Shayba 3:3094

Ubaydah ibn Humayd narrated to us, from Sinan ibn Habib, from Nabl bint Badr, from Salamah bint Aq'a, from Aisha, who said: "Indeed, the day of Friday is like the day of Arafah; the gates of mercy are opened in it, and in it is an hour during which the servant does not ask Allah for anything except that He gives it to him." It was said: "And which hour is it?" She said: "When the muezzin gives the call for the morning prayer."