Charles Ellicott Commentary 1 Corinthians 15:39

"All flesh is not the same flesh: but there is one [flesh] of men, and another flesh of beasts, and another flesh of birds, and another of fishes." — 1 Corinthians 15:39 (ASV)

All flesh is not the same flesh.—Better, There is no flesh the same flesh. All organisms have the same basis; there is a “structural unit” in all animal life, but God gives this a vast variety of form in humans, in beasts, and in fish. The same divine prescience that gives to all flesh here the form suited to its condition and surroundings can hereafter give it another form, suitable to the new conditions and surroundings in which it will then be placed. If we had only seen flesh in the form of an animal and were told that “flesh” could live in the sea, we might have equally argued, “How, with what body?” But as we see that there is a variety of bodies, we feel no such difficulty.