"I will forgive their wickedness
and remember their sins no more."
There will never be even the least mention of a believer's sins before God, either now or hereafter. Ezekiel writes of every godly man who turns to God and believes, "None of the offenses he has committed will be remembered against him." (Ezekiel 18:22)
By the way, let men be careful how they chide the people of God for any of their former sins. Perhaps you knew such a person before his conversion, and you say he was a liar or a drunkard. But now God has revealed His mercy to him in the pardon of his sins, and God says He will not mention them anymore. Take care how you cast their sins, committed in their times of ignorance, in their teeth, saying, "Oh, you are so holy now. Not very long ago I knew you when you were something else." Shall the God of heaven say He will not mention their sins any more, and yet you will do it? God will not take such insolence lightly!
It should be a great comfort to every believer that God will not remember their sins any more. He would have you remember them to humble you and renew your repentance, but He will not remember them to rebuke you with them--nor would He have others do it.
Oh what a comfort and a privilege this is! No matter how wicked or despicable you were, God will never remember your sin any more. This may be a mighty encouragement for men and women to believe and turn from all their sins. Although you may have been vile, abominable, and wicked, yet if you will believe, God will never mention any of your wickedness. More than that--they shall never be mentioned because they will have been forgotten.