وَمَا تِلْكَ بِيَمِينِكَ يَا مُوسَىٰ
And what is that in your right hand, O Moses?
Given the speaker's knowledge, the rhetorical role of the question is not simply to acquire information. The form draws the addressee into speech, focuses attention and prepares what follows. An apparently unknowing question can thus serve a specific communicative aim concerning a known matter.
The term tajāhul al-ʿārif must not be taken to attribute actual ignorance contrary to the theological or narrative context. Its basis is the question's form and purpose. The analytical error is to assume either that all interrogatives seek unknown information or that every question automatically exemplifies this figure.