Musnad Ahmad 33:1167

'Affan narrated to us, Wuhayb narrated to us, 'Abdullah ibn 'Uthman ibn Khuthaym narrated to us, from 'Abd al-Rahman ibn Sabit, from Jabir ibn 'Abdullah, who said: He narrated to us that the Messenger of Allah (peace and blessings of Allah be upon him) said: "O Ka'b ibn 'Ujrah, I seek refuge for you with Allah from the leadership of the foolish." He said: "And what is that, O Messenger of Allah?" He said: "Leaders who will come after me; whoever enters upon them, and believes their lies, and assists them in their oppression, then they are not of me, and I am not of them, and they shall not come to me at the Basin (al-Hawd). And whoever does not enter upon them, and does not believe their lies, and does not assist them in their oppression, then those are of me, and I am of them, and those shall come to me at the Basin." "O Ka'b ibn 'Ujrah, prayer is a means of nearness, fasting is a shield, and charity extinguishes sin just as water extinguishes fire." "O Ka'b ibn 'Ujrah, no one shall enter Paradise whose flesh has grown from unlawful gain; the Fire is more fitting for him." "O Ka'b ibn 'Ujrah, people go out in the morning in two ways: one who goes out selling his soul, thereby ruining his neck; and one who goes out buying his soul, thereby freeing his neck."