Pausing at the ending helps explain how Qurʾānic fawāṣil sound. At a pause, some case endings are not pronounced, and the audible end of a word may differ from its fully inflected form. Apparent differences of inflection do not always destroy the perceived harmony.
At the opening of Sūrat al-Fīl:
«أَلَمْ تَرَ كَيْفَ فَعَلَ رَبُّكَ بِأَصْحَابِ الْفِيلِ أَلَمْ يَجْعَلْ كَيْدَهُمْ فِي تَضْلِيلٍ»
Have you not seen what your Lord did to the people of the elephant, and how He made their plot fail?
The correspondence between “al-fīl” and “taḍlīl” is audible at the verse endings.