John Gill Commentary Leviticus 24:21

"And he that killeth a beast shall make it good: and he that killeth a man shall be put to death." — Leviticus 24:21 (ASV)

And he that killeth a beast, he shall restore it
The same as in (Leviticus 24:18), which is repeated for the confirmation of it, and that it might be observed, though Jarchi takes it to be a different law; before, he says, it speaks of him that kills a beast, here of him that makes any wound or bruise in it, which he must make good; and it must be allowed that the manner of expression is different; there it is, he that smites the soul of a beast so that it dies, here only he that smites a beast, though it dies not, yet having some damage done it, satisfaction must be made:

and he that killeth a man, he shall be put to death ;
or he that smites a man, though he does not kill him, as Jarchi observes, only makes a wound or bruise in him, because it is not said, the soul of a man, as before; but such damages did not require death, but satisfaction in another way, as in (Leviticus 24:19).