Rashi on Genesis 1:22/רש"י על בראשית א׳:כ״ב

1ויברך אותם AND HE BLESSED THEM — Because people decreased their number, hunting them and eating them, they needed a blessing (Genesis Rabbah 11:2); it is true that beasts also were in need of a blessing, but on account of the serpent that was to be cursed in the future, He did not bless them, in order that it might not be included in the blessing.

2פרו BE FRUITFUL — פרו is of the same root as פרי, and means bring forth fruit.

3ורבו AND MULTIPLY — Had He said “Be fruitful” only, one creature might have brought forth a single one, and no more, therefore He added ורבו “and multiply”, implying that one should bring forth many.