Tafsir of Al-Fath 48:3

(And Allah may help you): The manifestation of the Exalted Name [Allah] alongside the [mention of] help—it is said—is because it is the conclusion of the reasons or purposes, and to demonstrate the perfection of [His] concern for his [the Prophet’s] affair, as is indicated by the succeeding phrase: (a mighty help).

Al-Sadr said: The Name was manifested at the beginning [of the Surah] and here, because forgiveness relates to the Hereafter, while help relates to the worldly life. Thus, it is as if by attributing forgiveness and help to His explicit Exalted Name, it is indicated that Allah—Mighty and Majestic is He—is the One who manages your affairs in the worldly life and the Hereafter.

The Imam said: The Name of Majesty was manifested here to indicate that help comes only from Allah—Exalted be He—as He said: "And victory is not except from Allah." This is because victory comes through patience, and patience comes through Allah; He said: "And your patience is not but through Allah," for it is the stillness and tranquility of the heart, and that is through the remembrance of Allah: "Verily, in the remembrance of Allah do hearts find rest."

As for "mighty" (‘aziz), according to the apparent meaning, it is the one who is helped (al-mansur). Since it is used to describe the help itself, it is either:

1. Denoting relationship, even if the well-known forms for this are fi‘ali or fa‘ali like bazzaz—meaning a help containing might and strength.
2. Or there is a metaphor in the attribution, according to the rule of describing the infinitive with the passive participle—which is the one helped here—similar to [the phrase] "painful punishment" (‘adhabun alim), in one view.
3. Or it refers to the Doer [the Helper], because it has been said that [describing the help as 'mighty'] is not appropriate for the context and yields little benefit, since the speech concerns the state of the addressee who is helped, not the Speaker who is the Helper—though there is some objection to this.
4. It is also said: The speech is based on the estimation of an omitted word, meaning "its possessor is mighty," which is the one helped. But this involves the strain of omission and addition.

It may be said: There is no need for anything of what has been mentioned, for there is no barrier to describing the "help" as "mighty" according to its apparent meaning, based on one of the meanings of ‘izzah (might/rarity): the scarcity of existence or attainment. The meaning would be: Allah will help you with a help the likes of which are rare in existence and difficult to attain. Al-Raghib mentioned this regarding the verse: "And indeed, it is a mighty Book." I have seen this attributed to Al-Sadr after I had written it down from Al-Sadr; so contemplate this, and do not be of those who are weak [or incapable].