Tafsir of Al-Qasas 28:35

(He said, "We will strengthen your arm with your brother") is a response to his request, which—as some have said—refers back to his statement: "Send him with me..." The meaning is: We will strengthen you through him and assist you. The "strengthening of the arm" is a metonymy (kinaya) for empowering him, because the hand derives its strength from the ’adud (the upper arm, between the elbow and the shoulder), and the entire body derives its strength from the hand. There is no obstacle to interpreting it literally, as "with your brother" is not included in what is treated as a metonymy. Alternatively, it may be a representational metaphor (isti'ara tamthiliyya), where the state of Moses, peace be upon him, being strengthened by his brother, is likened to the state of a hand being strengthened by a powerful arm. It is also permissible that it is a synecdoche (majaz mursal) based on mentioning the cause in place of the effect via two degrees—the original meaning being "We will strengthen you through him," then "We will support you," then "We will strengthen your arm through him."

Zayd ibn Ali and al-Hasan recited it ‘ududuka with two dammahs. It is reported from al-Hasan that he read it with a dammah on the 'ayn and a sukun on the dad. Isa read it with both letters fatha. Others read it with a fatha on the 'ayn and a kasrah on the dad. It is also said that it may be ‘adud with a fatha on the 'ayn and sukun on the dad, though I know of no one who recited it as such.

His saying, Exalted is He, (And We will give you both authority) means great dominance and victory. This also refers back, as some have said, to his statement: "Indeed, I fear they will deny me."

His saying, Glorified is He, (So they will not reach you both) is a consequence of the realization of his intent; meaning: they will not reach you with conquest or by prevailing in argument.

(Through Our signs) is connected to a suppressed verb that has been made explicit in other places, meaning: "Go forth with Our signs." Or it is connected to "We will make," meaning: We will grant you authority by means of Our signs. Or it is connected to "authority" because it contains the meaning of dominance and victory. Or it is connected to the negation, according to the view of those who allow a prepositional phrase to be connected to the negative particle.

Al-Zamakhshari said: It is possible that it is an oath, the response of which is "they will not reach you," placed before the oath. Or, it is of the type of oath inserted into speech merely for emphasis, in which case it requires no response at all. The objection to the first view is that the response to an oath does not precede it, nor is it joined with fa. Perhaps he meant that it points to the response, and the response itself is suppressed, but he was lax in his expression. It is also permitted that it is a relative clause (sila) for a suppressed term, explained by "the victors" in His saying, "You and those who follow you are the victors," or it is a relative clause where the lam is for definition (al-ta'rif), not in the sense of "the one who" (alladhi). Or it is in that sense, according to the opinion of those who permit the prepositional phrase within the scope of the relative clause to be placed before the relative noun, whether absolutely or when the fronted element is an adverb (zarf). Its placement at the front is either for the sake of the rhyming interval (fasila) or for restriction (hasr).