The duty you are bound to do purifies you; to drop it in confusion is renunciation only in name.

For the seeker whose inner instrument still needs cleansing.

Here the obligatory rite is the presently active means to a purified mind, and it carries no genuine flaw of its own. One extant defense meets the objection that even required rites, involving harm to grain or to animal life, might be flawed for that reason: wherever a specific scriptural command reaches, the general prohibition against harm has no further room to operate, since the command aims only at a true human good. The single exception is a rite like shyena, sought only to harm another, where the fruit itself is calamity and the general ban reasserts itself. Outside that exception, dropping the required rite can only spring from an inverted seeing, mistaking the pure for the impure, which is precisely what tamas names.

For the one whose realization of Brahman depends on a chain kept unbroken.

Carry the obligatory and occasional rites, the great sacrifices among them, for as long as the body lasts, for the sake of knowledge of Brahman. Bodily life depends on the food left over from sacrifice; eating without offering is eating sin, and wrongly eaten food feeds the mind wrongly. Since the mind is made of food, pure food makes the being pure, a pure being steadies memory, and steadied memory alone loosens the knots that block realization. The rites that sustain this chain are therefore not to be set down, and doing so from the delusion that they bind is exactly the dark error the verse names.

Honestly marked as a gap, not a suppressed reading.

No comment from Madhva survives on this particular verse, and the published source states this directly rather than offering a substitute in his voice. What can honestly be said is a clearly labeled extension of his broader frame found elsewhere: since the self's capacity to act is always a dependent, granted competence rather than an owned power, mistaking that borrowed capacity for something one may simply set aside at will would, on that frame, be one more form of the confusion this verse condemns. This remains an extrapolation, offered as such, not Madhva's recorded word.

Read within a block rather than as a comment on this verse alone.

Abhinavagupta's surviving Gitartha-samgraha treats verses 18.4 through 18.11 together as one continuous passage rather than addressing 18.7 in its own separate wording. Within that span he lays out the Sankhya and Mimamsa positions on whether flawed or harmful action must be abandoned, and observes that the act of renouncing itself takes on the color of whichever guna moves it, sattvic, rajasic, or tamasic. This is the frame his extant comment actually offers; the verse's own tamasic case would sit inside it, though no comment addressed to 18.7 by itself survives.

For the one weighing whether a duty owed to one's station may be released.

Mark off two kinds of action clearly. Action taken up for a particular desire binds, and that may rightly be renounced. The perpetual duty owed to one's own station is different: it purifies the inner being as it is performed and becomes, by that purifying, itself a means to release. To apply the general praise of renunciation to this second kind of action, and drop it too, can spring only from confusion, and confusion belongs to tamas. So this particular giving-up, however it presents itself, is the dark kind.

A procedural account of how the confusion actually happens.

Read through the careful defense of the obligatory rite, the practical point is this: a specific injunction and a general prohibition are not automatically at war; each has its own field, and the confusion this verse condemns is precisely the failure to keep those fields distinct, so that the enjoined starts to look forbidden and the pure starts to look impure. That inversion, seeing a thing as its own opposite, is offered as tamas defined with unusual precision rather than left as a vague mood.