Thomas Aquinas

“ It is not a sin to covet God's likeness as to knowledge, absolutely; but to covet this likeness inordinately, that is, above one's measure, this is a sin. Hence Augustine commenting on Ps. 70:18, "O God, who is like Thee?" says: "He who desires to be of himself, even as God is of no one, wishes wickedly to be like God. Thus did the devil, who was unwilling to be subject to Him, and man who refused to be, as a servant, bound by His command."
Reply to Objection 3: This argument considers the likeness of equality.
Art. 3 - Whether the sin of our first parents was more grievous than other sins? ”

“ Also, among the inward movements, the appetite is moved towards the end before being moved towards that which is desired for the sake of the end; and consequently man's first sin was where it was possible for his appetite to be directed to an inordinate end. Now man was so appointed in the state of innocence, that there was no rebellion of the flesh against the spirit. Wherefore it was not possible for the first inordinateness in the human appetite to result from his coveting a sensible good, to which the concupiscence of the flesh tends against the order of reason. ”

“ It would seem that the first man's pride did not consist in his coveting the Divine likeness. For no one sins by coveting that which is competent to him according to his nature. Now God's likeness is competent to man according to his nature: for it is written (Gn. 1:26) : "Let us make man to our image and likeness." Therefore he did not sin by coveting God's likeness.
Objection 2: Further, it would seem that man coveted God's likeness in order that he might obtain knowledge of good and evil: for this was the serpent's suggestion: "You shall be as Gods knowing good and evil." ”