Musnad Abu Ya'la al-Mawsili 117:240

Zuhayr narrated to us, Affan narrated to us, Hammad narrated to us, Thabit narrated from Anas, that the Messenger of Allah (may Allah bless him and grant him peace) said: "Align yourselves, align yourselves. For by Allah, I surely see you from behind me just as I see you from in front of me."