As-Salaam alaikum,
Jabir Ibn Abdullahi, may Allah be pleased with him, narrated that once a person came to the Prophet, Sallallahu alaihi Wasallam, and said :-- "My Sins, my sins"! So, the Prophet, Sallallahu alaihi Wasallam said to him, say:-

"ALLAHUMMA MAGHFIRATUKA AWSA'U MIN ZUNUBI, WA RAHMATUKA ARJA INDI MIN AMALEE - O Allah, Your Forgiveness is more vast than my sins, and I am more hopeful of Your mercy than my good deeds." (Mustadrak Hakim, vol 1, page 543/544).