Istikhdām uses a word with more than one related sense and then employs a pronoun referring to it in another sense, or otherwise shifts the intended sense across connected references.
«إِذَا نَزَلَ السَّمَاءُ بِأَرْضِ قَوْمٍ رَعَيْنَاهُ وَإِنْ كَانُوا غِضَابًا»
“If the sky descends upon a people’s land, we graze on what it brings forth even if they are angry.”
Al-samāʾ refers to rain; the pronoun in raʿaynāhu is understood with reference to its resulting vegetation. This shift in the related sense is the rhetorical point.