Ziyad bin Abi Maryam (may Allah have mercy on him) narrates from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) that he said: "Remorse is repentance, and the one who repents is like one who has no sin."
Abd al-Razzaq narrated it thus from Ma'mar, munqati' (with a broken chain) and mawquf (as the Companion's own words), with its addition.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الشهادات / 20560