Musnad Abu Ya'la al-Mawsili 140:51

Abu Ibrahim al-Turjumani, Isma'il ibn Ibrahim, narrated to us, 'Ubays ibn Maymun narrated to us, Yazid al-Raqashi narrated to us, from Anas, who said: The Messenger of Allah (ﷺ) said: "Is one of you not able to recite 'Say, He is Allah, [who is] One' (Surah al-Ikhlas) in a night? For it is equivalent to the entire Quran." He said: And he said: "People must have a leader (arif), and the leader is in the Fire." He said: And the policeman (shurti) will be brought on the Day of Resurrection, and it will be said to him: "Put down your whip and enter the Fire."