Calvin comments on whether or not Judas received the body of Christ at the Last Supper.
When he says that he dwelleth in us, [John 6:56] the meaning is the same as if he had said, that the only bond of union, and the way by which he becomes one with us, is, when our faith relies on his death. We may likewise infer from it, that he is not now speaking of the outward symbol, which many unbelievers receive equally with believers, and yet continue separated from Christ. It enables us also to refute the dream of those who say, that Judas received the body of Christ as well as the other apostles, when Christ gave the bread to all; for as it is a display of ignorance to limit this doctrine to the outward sign, so we ought to remember what I have formerly said, that the doctrine which is here taught is sealed in the Lord’s Supper. Now, it is certain, in the first place, that Judas never was a member of Christ; secondly, it is highly unreasonable to imagine the flesh of Christ to be dead and destitute of the Holy Spirit; and, lastly, it is a mockery to dream of any way of eating the flesh of Christ without faith, since faith alone is the mouth — so to speak — and the stomach of the soul.
Here is another quote from Calvin’s commentary on John 6.
And I will raise him up at the last day [John 6:54] It ought to be observed, that Christ so frequently connects the resurrection with eternal life, because our salvation will be hidden till that day. No man, therefore, can perceive what Christ bestows on us, unless, rising above the world, he places before his eyes the last resurrection From these words, it plainly appears that the whole of this passage [John 6:52-59] is improperly explained, as applied to the Lord’s Supper. For if it were true that all who present themselves at the holy table of the Lord are made partakers of his flesh and blood, all will, in like manner, obtain life; but we know that there are many who partake of it to their condemnation. And indeed it would have been foolish and unreasonable to discourse about the Lord’s Supper, before he had instituted it. It is certain, then, that he now speaks of the perpetual and ordinary manner of eating the flesh of Christ, which is done by faith only. And yet, at the same time, I acknowledge that there is nothing said here that is not figuratively represented, and actually bestowed on believers, in the Lord’s Supper; and Christ even intended that the holy Supper should be, as it were, a seal and confirmation of this sermon. This is also the reason why the Evangelist John makes no mention of the Lord’s Supper; and therefore Augustine follows the natural order, when, in explaining this chapter, he does not touch on the Lord’s Supper till he comes to the conclusion; and then he shows that this mystery is symbolically represented, whenever the Churches celebrate the Lord’s Supper, in some places daily, and in other places only on the Lord’s day.