Will Allah punish a servant for a sin from which he has repented, and how does a servant know that his repentance has been accepted?

If a servant repents with a complete and fulfilled set of conditions, Allah the Almighty has promised to accept it, pardon them, and replace their evil deeds with good ones, as stated in the verses of Surat Al-Ma'idah, Taha, Al-Furqan, and Ash-Shura. Allah has forbidden us from despairing of His mercy and has promised forgiveness for all sins to whoever repents from them, in fulfillment of His saying: {Say, "O My servants who have transgressed against themselves [by sinning], do not despair of the mercy of Allah. Indeed, Allah forgives all sins. Indeed, it is He who is the Forgiving, the Merciful."} And "The one who repents from a sin is like one who has no sin." The acceptance of repentance is a matter of the unseen. What is required of the servant is to fulfill its conditions and to have a good opinion of Allah, while also fearing that it might not be complete. Steadfastness after repentance is a sign of its acceptance.