لم تكن الخردلة أصغر من الجبل
A mustard seed would not be smaller than a mountain.
The argument says that if every body were an actually assembled infinity of further-divisible parts, both a seed and a mountain would contain infinitely many. How then could one be genuinely less in size?
Two premises require scrutiny: 1. unlimited divisibility entails an already-existing infinity of constituents; 2. any two purported infinite collections must be equal in measurable size. Both are contested, so the example is not itself the conclusion.