«إِذَا نَزَلَ السَّمَاءُ بِأَرْضِ قَوْمٍ رَعَيْنَاهُ وَإِنْ كَانُوا غِضَابَا»
If rain falls upon a people’s land, we will graze it even if they are angry.
Al-samāʾ here denotes rain: the verb nazala suits rainfall. In raʿaynāhu (“we will graze it”), however, the pronoun activates the sense of the vegetation or pasturage brought about by that rain, which can actually be grazed. Rain itself cannot be grazed.
Thus the overt word and its pronoun point to distinct, related senses: a standard instance of the first form of istikhdām.