«أَوْ شِبْهِ تَضَادٍ كَالسَّمَاءِ وَالْأَرْضِ»
Or something resembling opposition, such as sky and earth.
Sky and earth are distinct entities, not two positive qualities competing to occupy exactly the same subject. Yet the imagination of height and depth evokes their opposition.
This is quasi-opposition, not strict contrariety. Rhetorical association may arise from a comparison that resembles opposition without satisfying all its logical conditions.