وَإِذَا تُلِيَتْ عَلَيْهِمْ آيَاتُهُ زَادَتْهُمْ إِيمَانًا
When His verses are recited to them, those verses increase them in faith. (Al-Anfāl 8:2)
The verb “zādat-hum” is assigned to “His verses.” Increased faith takes place under God's agency, while hearing the verses provides the occasion and instrumental cause through which that increase occurs.
Attributing the increase to the verses highlights their effect on believers. The causal association makes the indirect predication intelligible.