Musannaf Ibn Abi Shayba 21:134

Abu al-Ahwas narrated to us, from Mansur, from al-Hakam, from Abd al-Rahman ibn Abi Layla, from Ka’b, who said: "There are 'mu'aqqibat' (follow-up phrases), the one who says them will not be disappointed." Then he mentioned the like of the hadith of Waki’.