Musannaf Ibn Abi Shayba 37:636

Yahya ibn Ishaq narrated to us, he said: Yahya ibn Ayyub informed me, from Abu Qubayl, from Yuthay', from al-Nu'man ibn Bashir, that he said: "Send [an army] to the 'Amalah, for they are causing corruption in the land." Ka'b al-Ahbar said to him: "Refrain, do not do that. For it is in the revealed Book of Allah that there is a people who will be called the 'Amalah; they will carry in their hands whips like the tails of cattle. They will not smell the fragrance of Paradise. So do not be the first to send [an army] against them." He said: So he refrained. I (the narrator) said to Yahya: "What are the 'Amalah?" He said: "You call them the Shurtah (police) in Iraq."