Musnad Ahmad 907:218

Waki’ narrated to us, Al-A’mash narrated to us, from Al-Musayyab ibn Rafi’, from Tamim ibn Tarfah Al-Ta’i, from Jabir ibn Samurah Al-Suwa’i, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Will you not line up as the angels line up before their Lord?" We said: "O Messenger of Allah, and how do the angels line up before their Lord?" He said: "They complete the first rows, and they stand close together in the row."