Thomas Aquinas, Compendium of Theology

The further inference clearly follows that all perfections found in anything at all must originally and superabundantly be present in God. Whatever moves something toward perfection, must first possess in itself the perfection it confers on others. Thus a teacher has in his own mind the knowledge he hands on to others. Therefore, since God is the first mover, and moves all other beings toward their perfections, all perfections found in things must pre-exist in Him superabundantly.

Besides, whatever has a particular perfection but lacks another perfection, is contained under some genus or species. For each thing is classed under a genus or a species by its form, which is the thing's perfection. But what is placed under species and genus cannot be infinite in essence; for the ultimate difference whereby it is placed in a species necessarily closes off its essence. Hence the very ratio or description that makes a species known is called its definition, or even finis. Therefore, if the divine essence is infinite, it cannot possess merely the perfection of some genus or species and be lacking in other perfections; the perfections of all genera or species must be in God.