1 Corinthians 15:39

However, he is not content with this, but seeks another difference greater and more manifest. For that thou mayest not, when hearing, as I said, that all rise again, suppose that all enjoy the same reward; he laid before even in the preceding verses the seeds of this thought, saying, "But each in his own order." But he brings it out here also more clearly, saying, "All flesh is not the same flesh." For why speak I, saith he, in respect of seeds? In respect of bodies let us agitate this point, concerning which we are discoursing now. Wherefore also he addeth, and saith, "But there is one flesh of men, another flesh of beasts, another of birds, and another of fishes." "There are also celestial bodies, and bodies terrestrial; but the glory of the celestial is one, and the glory of the terrestrial is another." "There is one glory of the sun, and another glory of the moon, and another glory of the stars: for one star differeth from another star in glory." And what means he by these expressions? Wherefore from the resurrection of the body did he throw himself into the discourse of the stars and the sun? He did not throw himself out, neither did he break off from his purpose; far from it: but he still keeps to it. For whereas he had established the doctrine concerning the resurrection, he intimates in what follows that great will be then the difference of glory, though there be but one resurrection. And for the present he divides the whole into two: into "bodies celestial," and "bodies terrestrial." For as the disbelief of the resurrection makes men supine, so again it makes them indolent to think that all are vouchsafed the same reward. Wherefore he corrects both. And the one in the preceeding verses he had completed; but this he begins now. […]

975. – Here the Apostle presents an example of the diverse qualities of a rising body in diverse species. First, by comparing heavenly to earthly bodies; secondly, earthly to heavenly (v. 40b); thirdly, celestial bodies to each other (v. 41). 976. – Because someone could …

Lest you, having heard about wheat, should think that just as all its ears grow alike, so too in the resurrection all will be alike, he wishes to show that there will be a difference among the risen (which he also hinted at before with …

All flesh is not the same flesh,....

All flesh is not the same flesh - This verse and the following are designed to answer the question 1Co 15:35, “with what bodies do they come?” And the argument here is, that there are many kinds of bodies; that all are not alike; that while they are bodies, yet they partake of different qualities, forms, and properties; and that, therefore, it is not absurd to suppose that God may transform the human body into a different form, and cause it to be raised up with somewhat different properties in the future world.

He implies by the word that our resurrection bodies shall be in some sense really flesh, not mere phantoms of air [ESTIUS]. So some of the oldest creeds expressed it, "I believe in the resurrection of the flesh." Compare as to Jesus' own resurrection body, Lu 24:39;

All flesh is not the same flesh - Though the organization of all animals is, in its general principles, the same, yet there are no two different kinds of animals that have flesh of the same flavour, whether the animal be beast, fowl, or fish. And this is precisely the same with vegetables. In opposition to this general assertion of St. Paul, there are certain people who tell us that fish is not flesh; and while their religion prohibits, at one time of the year, the flesh of quadrupeds and fowls, it allows them to eat fish, fondly supposing that fish is not flesh: they might as well tell us that a lily is not a vegetable, because it is not a cabbage. There is a Jewish canon pronounced by Schoettgen which my readers may not be displeased to find inserted here: Nedarim, fol. 40: הנודר מן הבשר יהא אסור בבור רגים והגים He who is bound by a vow to abstain from flesh, is bound to abstain from the flesh of fish and of locusts. From this it appears that they acknowledged that there was one flesh of beasts and another of fishes, and that he was religiously bound to abstain from the one, who was bound to abstain from the other.