The curse follows him until the Day of Recompense.
A refusal that does not stay in the past
Ibn Kathir says Iblis was told he would be followed by a curse that would hound him until the Day of Resurrection. One refusal, never repented, became a lasting state. He never asks forgiveness in this scene.
A grudge you kept from school. A habit you never quit, first one cigarette, then years. What you refuse to undo keeps walking with you. The difference for you is that the door to repent is open.
That thing I did was long ago, it does not matter now.
An unrepented wrong does not stay in the past; it follows, unless I turn back.
Pick one old wrong you never asked forgiveness for, and ask Allah for it tonight.