Musannaf Ibn Abi Shayba 3:1439

Abu al-Ahwas narrated to us, from Abu Ishaq, from al-Aizar, from Abu Basir, who said: Ubayy ibn Ka'b said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Verily, the first row is like the row of the angels. And if you knew [its virtue], you would have raced toward it."