Tafsir of An-Nisa' 4:39

(And what harm would come to them) means: What would be upon them, or what misfortune and harm would befall them, (if they believed in Allah and the Last Day and spent)—upon those mentioned among the groups—[seeking] the Face of Allah, the Exalted, as the context implies and the speech conveys, (from what Allah has provided them) of wealth.

The intent is not to ask about the harm resulting from belief and spending in the way of Allah, as is apparent, for there is no harm in that to be asked about. Rather, the intent is to rebuke them for their ignorance regarding where the benefit lies and for holding beliefs contrary to reality, and to incite them to direct their thoughts toward obtaining an answer—perhaps it will lead them to know the advantages therein, which are more useful than dispersing one's efforts. It also serves to alert them that one who is invited to a matter in which there is no harm ought to respond out of caution, so how much more so if benefits flow from it? This is an ingenious style frequently used by the Arabs in their speech. Among such examples is the saying: "What harm would it have done you if you had shown favor, even if it were a youth who is enraged and wrathful?"

In this speech, there is a rebuttal to the Jabriyyah (Determinists), for such things are not said to one who has no choice and no influence at all over his actions. Do you not see that if one were to say to a blind person, "What harm would it do you if you were sighted?" or to a short person, "What harm would it do you if you were tall?", one would be attributed to that which is disliked.

Those who permit the faith of the Muqallid (imitator) also use this as evidence, as it implies that faith is of the utmost ease; had deduction (istidlal) been obligatory, it would have been of the utmost difficulty. It was answered—after conceding the implication—that the difficulty lies in the details, which are not obligatory; as for the proofs in a general sense, they are easy and are what is obligatory.

(If) is either used in its literal sense, and the speech is construed according to the meaning—i.e., if they had believed, it would not have harmed them—or it is in the sense of an (that) which acts as an infinitive particle, as Abu al-Baqa’ said. Under both interpretations, it is not a new beginning (isti'naf). It is also permitted that the sentence be a new beginning, with its response being implied, i.e., "they would have attained happiness," or similar.

Faith was mentioned first here, while it was mentioned later in the preceding verse, because there it was mentioned to explain why their expenditures in this world were misplaced, whereas here it is for the purpose of incitement; therefore, it is appropriate to begin with the most important and then the next in importance. If it were said that faith was delayed and spending brought forward because that spending was in the sense of extravagance, which is the counterpart of stinginess—so faith was delayed so as not to separate the two counterparts—that would also have merit, especially if we hold the view of conjunction.

(And Allah has ever been, concerning them, Knowing) is a predicate containing a threat and an alerting to the evil of their inner selves, and that He, the Exalted, is aware of what they have hidden within themselves, so He will recompense them for it. It is also said: It contains an indication of His rewarding them had they believed and spent. There is no harm in intending that He was knowing of them, their actual states, and their hypothetical states, so He punishes for the former and rewards for the latter, as His, the Exalted’s, saying suggests...