The one thing that keeps this path shut is the trust you have not yet given it.

Read through Shankara, as knowledge of the Self refused.

For Shankara, the dharma here is the knowledge of the Self, and the faithless are those who have quietly settled into the view that the body alone is the Self, living only to feed their own appetites, their minds spoiled by arguments set against the very foundation the teaching rests on. Because they have set aside the means scripture actually prescribes and rely only on methods their own intellect has invented, they miss not only the final goal but even the preliminary devotion that stands as a first step toward it. What they are left with, in his phrase, is the road of death and rebirth running on through hellish and animal births, the plain cost of the missing trust rather than any added penalty.

Read through Ramanuja, as a great wonder at the door already open.

For Ramanuja, the dharma is the worship of Krishna himself, supremely dear, and the worship offered to him supremely dear in turn, a means to the highest good that, once undertaken, never perishes. He calls the failure of the faithless a great wonder for a precise reason: these are not people barred by distance or difficulty. They have already reached the very condition fit for taking up this worship, and still, lacking the trusting eagerness to enter it, they remain circling on the path of rebirth. Nothing stood between them and the goal except the trust they did not give.

Read honestly, as a gap the source does not fill.

The published record for Madhva's commentary on this exact verse says only that he offers none. Nothing more should be claimed here in his name. What can be noted, carefully marked as inference and not report, is that Madhva's broader emphasis elsewhere in the Gita falls on the soul's total dependence on the Lord for every capacity it has, including whatever capacity makes trust possible. That pattern would fit comfortably with this verse's picture of faithlessness as the soul's own unfitness, but it remains a guess about his method, not a reading of words he actually left behind on 9.3.

Read from a single surviving line, extended only as clearly-marked conjecture.

What survives from Abhinavagupta here is one terse gloss: those without faith return, meaning they are born and die again and again. That is the whole of it. On a Kashmir Shaiva reading, one might cautiously extend this: faithlessness as a further contraction of the very freedom consciousness already is, a forgetting so complete that even the invitation to recognize one's own nature fails to register, so the wheel simply turns on by default. This extension is offered plainly as extrapolation, built to stay consistent with his wider philosophy, not as a report of anything he wrote on this verse.

Read through Sridhara, as an open door refused.

Sridhara opens by asking the very question this verse answers: if the path is this easy, who remains bound? He reads the dharma at stake as devotion joined with knowledge, and answers that some people withhold trust from this path even while pushing hard by other methods of their own choosing. Their effort is real. What is missing is trust in the one means that would actually work, and because of that missing trust alone, they do not reach the goal. His closing image says it plainly: the door stands wide open, and those who will not walk through it are left pacing the wall outside, kept out by nothing but their own refusal.

Read through Madhusudana, as effort mistaken for trust.

Madhusudana frames the verse as answering an unspoken objection: if the path is so easy, why does not everyone take it up at once? His answer is that a mind spoiled by arguments run counter to the teaching's own foundation stops treating it as a valid means of knowing at all, however hard that same mind may then strive by methods it invents for itself. Effort of that kind, sincere as it may be, does not substitute for trust placed in the actual, prescribed means, and so it returns a person, certainly, to the ongoing round of birth and death rather than carrying them out of it.