كَلَّا لَيُنْبَذَنَّ فِي الْحُطَمَةِ
No indeed! He will surely be flung into the Crusher. (الهمزة: 4)
Kallā emphatically repudiates the preceding mistaken confidence. The discourse turns sharply from imagined permanence through wealth to an unavoidable consequence. Rebuke and reversal are central to the impact.
Treating kallā as an ordinary interchangeable lā misses its discourse function. The passage first presents the false assumption and then decisively rejects it, before specifying what actually awaits the person.