Sayyiduna Ka'b bin Ujrah (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) said to me: "O Ka'b bin Ujrah! I commend you to the protection of Allah from rulers who will come after me. Whoever frequents their doors, affirms them in their lies and helps them in their oppression, he is not of me and I am not of him. And whoever frequents their doors or does not, but does not affirm them in their lies and does not help them in their oppression, he is of me and I am of him, and he will soon come to me at the Pond (al-Hawd)."
"O Ka'b! Prayer is a proof, charity extinguishes sin just as water extinguishes fire, and fasting is a strong shield."
"O Ka'b! No flesh that has grown from unlawful earnings will enter Paradise. O Ka'b! Whatever flesh grows from unlawful earnings, the Fire is more deserving of it."
Hadith Referenceالمعجم الكبير للطبراني / باب الكاف / 16262