“Ammā” means: “Whatever there may be,” while “baʿdu” is an adverbial expression connected to the omitted verb “there may be,” together with its conditional particle. It is indeclinable with a ḍammah ending, though functioning in the accusative, because the noun to which it is annexed has been omitted while its meaning is intended. Such adverbs—“baʿdu” and others like it—are made indeclinable with a ḍammah ending when the annexed noun is omitted but its meaning remains intended, as in the saying of Allah, Most High: “To Allah belongs the command before and after.” [al-Rūm: 4]

Thus, this is an abridgment in fiqh, ………………

His statement, “an abridgment”: it is a passive participle derived from the form VIII verb.

The scholars have said: an abridgment is that whose wording is brief but whose meaning is abundant. (1)

His statement, “in fiqh”: linguistically, fiqh means understanding. An example is the saying of Allah, Most High: “But you do not understand their glorification.” [al-Isrāʾ: 44] And: “They said, ‘O Shuʿayb, we do not understand much of what you say.’” [Hūd: 91] That is, “We do not comprehend.”

In the Sacred Law, it means knowledge of Allah’s doctrinal and practical rulings.

Thus, fiqh in the Sacred Law is not confined to the actions of those legally accountable, or to practical rulings; rather, it even encompasses doctrinal rulings. Indeed, some scholars say that the knowledge of creed is the greater fiqh. (2) This is correct, for one cannot worship the One worshipped until one knows His oneness in His lordship, His divinity, and His names and attributes. How, otherwise, can one worship One who is unknown?!

For this reason, the first foundation is tawḥīd (the affirmation of Allah’s oneness), and it rightly deserves to be called the greater fiqh.

However, what the author means here is fiqh in its technical sense: knowledge of practical rulings based on their detailed evidences.