Musannaf Ibn Abi Shayba 33:1228

Affan narrated to us, he said: Abd al-Wahid narrated to us, from al-A'mash, from Mujahid, regarding the saying of the Exalted: "Repent to Allah with a sincere repentance," he said: It is that he repents, then he does not return [to the sin].