Musannaf Ibn Abi Shayba 37:311

Waki’ narrated to us, from Sufyan, from his father, from ‘Ikrimah, from his father, from Ibn ‘Abbas, who said: Ka’b said: "If you see that rain has been withheld, then know that the people have withheld the Zakat, so Allah has withheld what is with Him. And if you see that swords have been unsheathed, then know that the judgment of Allah has been neglected, so they have taken vengeance upon one another. And if you see that adultery has become widespread, then know that usury (riba) has become widespread."