B.B. Warfield is famous for his endorsement of Evolution from within the Reformed Church Tradition, and his ability to distinguish the agnosticism of Charles Darwin from Darwin's work as a Naturalist. All of Warfield's writings on Evolution have been assembled in an extremely helpful book edited by Mark A. Noll and David N. Livingstone, "B.B. Warfield: Evolution, Science and Scripture (selected writings)". The book contains Warfield's review of Darwin's letters and selections of his writings on the topic of evolution. One of the most helpful articles is Warfield's essay, "Calvin's Doctrine of Creation" where Warfield claims that "Calvin's doctrine of creation is [...] an evolutionary one."
"It should scarcely be passed without remark that Calvin's doctrine of creation is, if we have understood it aright, for all except the souls of men, an evolutionary one. The "indigested mass," including the "promise and potency" of all that was yet to be, was called into being by the simple fiat of God. But all that has come into being since - except the souls of men alone - has arisen as a modification of this original world-stuff by means of the interaction of its intrinsic forces. Not these forces apart from God, of course: Calvin is a high theist, that is, supernaturalist, in his ontology of the universe and in his conception of the whole movement of the universe. To him God is the prima causa omnium and that not merely in the sense that all things ultimately - in the world-stuff - owe their existence to God; but in the sense that all the modifications of the world-stuff have taken place under the directly upholding and governing hand of God, and find their account ultimately in His will. But they find their account proximately in "second causes"; and this is not only evolutionism but pure evolutionism. What account we give of these second causes is a matter of ontology; how we account for their existence, their persistence, their action - the relation we conceive them to stand in to God, the upholder and director as well as creator of them. Calvin's ontology of second causes was, briefly stated, a very pure and complete doctrine of concursus, by virtue of which he ascribed all that comes to pass to God's purpose and directive government. But that does not concern us here.
What concerns us here is that he ascribed the entire series of modifications by which the primal "indigested mass," called "heaven and earth," has passed into the form of the ordered world which we see, including the origination of all forms of life, vegetable and animal alike, inclusive doubtless of the bodily form of man, to second causes as their proximate account. And this, we say, is a very pure evolutionary scheme. He does not discuss, of course, the factors of the evolutionary process, nor does he attempt to trace the course of the evolutionary advance, nor even expound the nature of the secondary causes by which it was wrought. It is enough for him to say that God said, "Let the waters bring forth. . . . Let the earth bring forth," and they brought forth. Of the interaction of forces by which the actual production of forms was accomplished, he had doubtless no conception: he certainly ventures no assertions in this field. How he pictured the process in his imagination (if he pictured it in his imagination) we do not know. But these are subordinate matters. Calvin doubtless had no theory whatever of evolution; but he teaches a doctrine of evolution. He has no object in so teaching except to preserve to the creative act, properly so called, its purity as an immediate production out of nothing. All that is not immediately produced out of nothing is therefore not created - but evolved. Accordingly his doctrine of evolution is entirely unfruitful. The whole process takes place in the limits of six natural days. That the doctrine should be of use as an explanation of the mode of production of the ordered world, it was requisite that these six days should be lengthened out into six periods - six ages of the growth of the world. Had that been done Calvin would have been a precursor of the modern evolutionary theorists. As it is, he only forms a point of departure for them to this extent - that he teaches, as they teach, the modification of the original world-stuff into the varied forms which constitute the ordered world, by the instrumentality of second causes - or as a modern would put it, of its intrinsic forces. This is his account of the origin of the entire lower creation. (See Note 45.)"
#45. H. Bavinck in the first of his Stone Lectures ("The Philosophy of Revelation," 1909, pp. 9-10) remarks: "The idea of development is not a production of modern times. It was already familiar to Greek philosophy. More particularly Aristotle raised it to the rank of the leading principle of his entire system by his significant distinction between potentia and actus. . . . This idea of development aroused no objection whatever in Christian theology and philosophy. On the contrary, it received extension and enrichment by being linked with the principle of theism." Calvin accordingly very naturally thought along the lines of a theistic evolutionism.
B.B. Warfield, "Calvin's Doctrine of Creation",