وَكَذَٰلِكَ يَجْتَبِيكَ رَبُّكَ وَيُعَلِّمُكَ مِن تَأْوِيلِ ٱلْأَحَادِيثِ وَيُتِمُّ نِعْمَتَهُۥ عَلَيْكَ
Wa-kadhālika yajtabīka rabbuka wa-yuʿallimuka min taʾwīli'l-aḥādīthi wa-yutimmu niʿmatahu ʿalayka wa-ʿalā āli Yaʿqūba kamā atammahā ʿalā abawayka min qablu Ibrāhīma wa-Isḥāq
"'And thus will your Lord choose you, and teach you the interpretation of events, and complete His favour upon you and upon the family of Jacob, as He completed it before upon your forefathers Abraham and Isaac.'"
This verse was cited at al-Fatḥ 48/2 (wa-yutimma niʿmatahu ʿalayk), and the following note was entered there:
"Your Lord will choose you… and will complete His favour upon you and upon the family of Jacob" (Yūsuf 12/6) — at the beginning of the story, the sentence that announces its end.
And this is the most remarkable feature of the sūra as narrative technique. I record it as my own reading, and its ground is the order of the verses:
The sūra states the outcome plainly in the sixth verse. That is, the reader goes through the scenes of the casting into the well, the sale into slavery, the slander and the prison knowing the outcome. The tension has been taken away from the question "what will happen?" and given to the question "how will it happen?"
And this accords with the sūra's own key construction: taʾwīlu'l-aḥādīth — knowing where events arrive. The sūra gives the reader exactly this at the beginning of the story: the place that will be arrived at.
The concrete sense of the root: to gather a thing, to collect it, to bring it together. Jibāya — the collection of a tax. Form VIII (ijtibāʾ): to choose and gather to oneself, to set apart.
The lexicographers record the difference between this word and iṣṭifāʾ (selection) thus: ijtibāʾ also includes drawing the chosen thing near to oneself — not merely setting apart, but setting apart and gathering.
The مِن at the head of the construction must be recorded, and the lexicographers explain it as partitive (tabʿīḍ): "a portion of the interpretation of events".
I give this as my own reading, and its ground is the preposition: the promise is not an unbounded knowledge — it is a share. And the same particle stands in Joseph's own mouth in the hundred and first verse: wa-ʿallamtanī min taʾwīli'l-aḥādīth. That is, in the form the promise was given, in that same form thanks are given for it.
And a link with the axis of al-Kahf can be made here: al-Kahf treated the limit of knowledge across four stories (wa-lam tuḥiṭ bihi khubrā, 18/68). Sūrat Yūsuf sets the same limit with a single particle that states the measure of what is given.