تَاللَّهِ تَفْتَأُ تَذْكُرُ يُوسُفَ
By God, you will keep remembering Joseph.
The oath particle in “tallāhi” is less common than the more usual “wallāhi,” while “taftaʾu” is likewise a less frequent verb. Their uncommon character is mutually fitting in this particular utterance.
The point is not that obscurity is automatically beautiful; rather, the words occupy a coherent stylistic register, supporting the distinctive tone of the speech.