Sayyiduna Abu Tawil Shatab al-Mamdud (may Allah be pleased with him) narrates that he came to the Messenger of Allah (peace and blessings be upon him) and said: What is your view of a man who has committed all sins, leaving none of them, and in doing so left no desire, small or great, without fulfilling it; is there any repentance for him? He (peace and blessings be upon him) said: "Have you accepted Islam?" He said: As for me, I bear witness that there is no true deity except Allah, alone, without partner, and that you are the Messenger of Allah. He (peace and blessings be upon him) said: "Yes; do good deeds and abandon evil deeds, and Allah will turn all of them into good deeds for you." He said: And my betrayals and my acts of wickedness too? He (peace and blessings be upon him) said: "Yes." He said: Allahu akbar (Allah is the Greatest), and he kept saying the takbir until he disappeared from sight.
Hadith Referenceالمعجم الكبير للطبراني / باب الشين / 7204