Musannaf Ibn Abi Shayba 21:195

Waki’ narrated to us, from al-A’mash, from Abu Ishaq, from ‘Ubayd ibn ‘Amr al-Hazimi, from ‘Ali, who said: I do not consider anyone who possesses intellect and has entered into Islam to sleep until he recites the Verse of the Footstool (Ayat al-Kursi).