«وَسَمَاحُكَ يُغِيثُ وَسَمَاؤُكَ تُغِيثُ»
Your generosity brings rescue, and your sky brings welcome rain.
Samāḥ denotes liberality and samāʾ the sky. The closely sounding expressions join human generosity to the familiar life-giving image of rain. The paired verbs reinforce the sense of help or relief.
The rhetorical function is to show the patron's charity as widespread and beneficial, like rainfall. The words are not identical in meaning: the beauty comes from their sound proximity and the transfer of an image between two domains.