Thomas Aquinas

Rest is taken in two senses, in one sense meaning a cessation from work, in the other, the satisfying of desire. Now, in either sense God is said to have rested on the seventh day.
First, because He ceased from creating new creatures on that day, for, as said above (1, ad 3), He made nothing afterwards that had not existed previously, in some degree, in the first works; secondly, because He Himself had no need of the things that He had made, but was happy in the fruition of Himself. Hence, when all things were made He is not said to have rested "in" His works, as though needing them for His own happiness, but to have rested "from" them, as in fact resting in Himself, as He suffices for Himself and fulfils His own desire. And even though from all eternity He rested in Himself, yet the rest in Himself, which He took after He had finished His works, is that rest which belongs to the seventh day. And this, says Augustine, is the meaning of God's resting from His works on that day (Gen. ad lit. iv).
God ended: So that, according to our version of the Scripture, the completion of the works is attributed to the seventh day, though according to another (Septuagint) it is assigned to the sixth. Either version, however, may stand, since the completion of the universe as to the completeness of its parts belongs to the sixth day, but its completion as regards their operation, to the seventh.
It would seem that God did not rest on the seventh day from all His work. For it is said (John 5:17), "My Father worketh until now, and I work." God indeed "worketh until now" by preserving and providing for the creatures He has made, but not by the making of new ones.

When "the earth brought forth the green herb." But concerning the production of plants, Augustine's opinion differs from that of others. For other commentators, in accordance with the surface meaning of the text, consider that the plants were produced in act in their various species on this third day; whereas Augustine (Gen. ad lit. v, 5; viii, 3) says that the earth is said to have then produced plants and trees in their causes, that is, it received then the power to produce them. He supports this view by the authority of Scripture, for it is said (Genesis 2:4-5): "These are the generations of the heaven and the earth, when they were created, in the day that . . . God made the heaven and the earth, and every plant of the field before it sprung up in the earth, and every herb of the ground before it grew." Therefore, the production of plants in their causes, within the earth, took place before they sprang up from the earth's surface. And this is confirmed by reason, as follows. In these first days God created all things in their origin or causes, and from this work He subsequently rested. Yet afterwards, by governing His creatures, in the work of propagation, "He worketh until now."Now the production of plants from out the earth is a work of propagation, and therefore they were not produced in act on the third day, but in their causes only. However, in accordance with other writers, it may be said that the first constitution of species belongs to the work of the six days, but the reproduction among them of like from like, to the government of the universe. And Scripture indicates this in the words, "before it sprung up in the earth," and "before it grew," that is, before like was produced from like; just as now happens in the natural course by the production of seed. Wherefore Scripture says pointedly (Genesis 1:11): "Let the earth bring forth the green herb, and such as may seed," as indicating the production of perfection of perfect species, from which the seed of others should arise. Nor does the question where the seminal power may reside, whether in root, stem, or fruit, affect the argument.