كَلَّا سَوْفَ تَعْلَمُونَ ثُمَّ كَلَّا سَوْفَ تَعْلَمُونَ
No indeed, you will know; again, no indeed, you will know. (التكاثر: 3–4)
The warning returns with thumma before the second occurrence. This repetition is not idle lengthening: it impresses the message more forcefully and intensifies the rebuke. Thumma ordinarily suggests separation or delay, while rhetorical readings may also note an advance in the gravity of the warning.
Calling the two clauses meaningless duplication ignores the discourse movement. Equally, it is unwarranted to force thumma to denote two specifically dated events on grammatical grounds alone. Context determines the extent of chronological versus rhetorical sequencing.