قَالَ لَا تَخْتَصِمُوا لَدَيَّ وَقَدْ قَدَّمْتُ إِلَيْكُم بِالْوَعِيدِ
“He (Allah) will say: Don’t argue with each other before me and I have already presented to you the threat (or promise of punishment)”.
When people come and argue on the Day of Judgement Allah will declare to them that He had already presented to them the threat of punishment in the life of this world for those who rebel and disbelieve.
As such, there is no benefit for them to argue the matter now.
“Don’t argue with each other before me” — dispute is rejected on that Day.
“I have already presented to you the threat” — the warning was made clear in worldly life.
The threat concerns those who rebel and disbelieve.
Since the warning was given, arguing on the Day of Judgement brings no benefit.
“I have already presented to you the threat” — the message was conveyed beforehand.
People come and argue before Allah.
“Don’t argue with each other before me.”
There is no benefit to argue the matter now.