Tafsir of An-Nisa' 4:156

(And for their disbelief) is a conjunction to the previous “and for their disbelief”. Let it not be imagined that this is a conjunction of a thing to itself, or that there is no benefit in it; for the intended meaning of the conjoined disbelief is the disbelief in Jesus, peace be upon him, while the intended meaning of the disbelief upon which it is conjoined is either disbelief in the absolute sense or disbelief in Muhammad (may God bless him and grant him peace), due to its proximity to His saying—Exalted is He—: “Our hearts are wrapped.” God—Exalted is He—has narrated this statement from them in their confrontations with him (peace and blessings be upon him) in several places. Thus, the conjunction serves to indicate that each of the two instances of disbelief is individually capable of being a cause.

It may also be considered that the conjoined part refers to the total sum, and its distinctness from the individual part upon which it is conjoined is evident. Alternatively, it is a conjunction to “So for their breaking”. It is also permissible to consider the conjunction of the sum of this and what preceded it to the sum of what was before it; thus, the forbidden implication [of a tautology] is not to be imagined. Even if we were to assert that the disbelief is identical, the sum remains distinct from the sum, even if some of their parts do not differ from one another. It has been said that the disbelief in the three places is distinct by interpreting it in the latter two as we have indicated, and in the first instance as the disbelief in Moses, peace be upon him, due to its proximity to the breaking of the covenant and the aforementioned account of the transgression on the Sabbath.

(And their speaking against Mary a great slander), the extent of which cannot be estimated, as they attributed to her—far be it from her—that which she is in herself a million, million degrees removed from. They persisted in this, unconcerned by the manifestation of the miracle proving her innocence. “Slander” (buhtan) is a lie so intense and great that one is bewildered by it. It is in the accusative case because it is the direct object of “speaking”. It has also been permitted that it is an adjective for a deleted verbal noun, meaning: “a saying that is a slander”. It is also said that it is an infinitive in the place of a state (hal), meaning: “slandering”.