Musnad Ahmad 30:3172

I read to Abd al-Rahman: Malik, and Ishaq narrated to us, he said: Malik informed us, from Abu al-Zinad, from al-A'raj, from Abu Hurairah, that the Messenger of Allah, peace and blessings of Allah be upon him, mentioned Friday and said: "In it is an hour; no Muslim servant coincides with it while he is standing praying, asking Allah for something, but He will give it to him." And the Messenger of Allah, peace and blessings of Allah be upon him, gestured with his hand. Ishaq said: He indicated that it is short.