Musnad Ahmad 175:31

Ali ibn Ishaq narrated to us, he said: Abdullah informed us, he said: Zakariya ibn Abi Za'idah informed us, from Muhammad ibn Abd al-Rahman ibn Sa'd ibn Zurarah, from Ibn Ka'b ibn Malik al-Ansari, from his father, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Two hungry wolves sent into a flock of sheep are not more destructive to them than a man's greed for wealth and status is to his religion."