Musnad Ahmad 1098:12

'Affan narrated to us, Hammad ibn Salamah narrated to us, from Qays ibn Sa'd, from Muhammad ibn Ibrahim al-Taymi, from Abu Salamah ibn 'Abd al-Rahman, from Abu Hurayrah, who said: I came to al-Sham and met Ka'b. He would narrate to me from the Torah, and I would narrate to him from the Messenger of Allah (peace and blessings of Allah be upon him), until we came to the mention of Friday. I narrated to him that the Messenger of Allah (peace and blessings of Allah be upon him) said: "Indeed, there is an hour on Friday; no Muslim coincides with it while asking Allah for good, except that He gives it to him." Ka'b said: "Allah and His Messenger have spoken the truth. It is once every year." I said: "No." Ka'b looked for a while, then said: "Allah and His Messenger have spoken the truth. It is once every month." I said: "No." He looked for a while and said: "Allah and His Messenger have spoken the truth. It is once every Friday." I said: "Yes." Ka'b said: "Do you know which day it is?" I said: "And which day is it?" He said: "In it, Allah created Adam, and in it the Hour will be established, and the creatures are listening in it, except for the two heavy ones: the Jinn and Mankind, out of fear of the Resurrection." I came to Medina and informed 'Abd Allah ibn Salam of Ka'b's statement. He said: "Ka'b lied." I said: "He has returned to my view." He said: "Do you know which hour it is?" I said: "No." I insisted upon him: "Inform me, inform me!" He said: "It is between the 'Asr and the Maghrib." I said: "How, when there is no prayer?" He said: "Have you not heard the Prophet (peace and blessings of Allah be upon him) say: 'The servant remains in prayer as long as he is in his place of prayer, waiting for the prayer'?"