أَيَا شَجَرَ الْخَابُورِ مَالَكَ مُورِقًا، كَأَنَّكَ لَمْ تَجْزَعْ عَلَى ابْنِ طَرِيفٍ
O tree of al-Khabur, why are you leafy, as if you have not grieved for Ibn Tarif?
The poet knows that the tree’s greenness is natural. The question is not a real request for information; it performs grief, astonishment and reproach. This is tajahul al-ʿarif, speaking as though unaware of what one knows.
A genuine question seeks unknown information. This literary question draws force precisely from the speaker’s evident knowledge.