نُورُهُ مُسْتَفَادٌ مِنْ نُورِ الشَّمْسِ
Its light is derived from the light of the sun.
If the discussion concerns the moon, “its light” is readily understood as moonlight. Leaving “the moon” implicit can test how attentively the listener follows contextual signals.
This is testing whether, or how fully, the listener is attentive. It measures contextual understanding; it is not an invitation to produce arbitrary obscurity. With no sufficient clue, the omission would merely confuse.