פירוש על בראשית 1:21

התנינים THE HUGE CREATURES — the large fishes that are in the sea; and according to the statement of the Agada (Bava Batra 74b) it means here the Leviathan and its consort which He created male and female. He, however, killed the female and preserved it in salt for the benefit of the righteous in the time to come, for had they been permitted to be fruitful and to multiply the world could not have endured because of them.

התנינים הגדולים, even though, in the previous verse, the Torah reports on the directive for the waters to produce multiple reproductions of each species which has its habitat in the waters, and we could have thought that this did not include gigantic creatures such as whales, the fact is they (it) too had been produced by the waters at the same time. The species described as Leviathan, Nachash beriach and Leviathan beriach in Isaiah 27,1 and the Leviathan described in Job 40,25 are what our verse here refers to.

ויברא אלוקים את התנינים, the evolutionary powers of the waters did not suffice for this task. They could not produce the original sea-monsters without having been provided for this with seed by the Creator.