Therefore, though the impious make a noise, there is nothing justly to offend us in this mode of speaking by which Moses describes Satan, the prince of iniquity, under the person of his servant and instrument, at the time when Christ, the Head of the Church, and the Sun of Righteousness, had not yet openly shone forth. Add to this, the baseness of human ingratitude is more clearly hence perceived, that when Adam and Eve knew that all animals were given, by the hand of God, into subjection to them, they yet suffered themselves to be led away by one of their own slaves into rebellion against God. As often as they beheld any one of the animals which were in the world, they ought to have been reminded both of the supreme authority, and of the singular goodness of God; but, on the contrary, when they saw the serpent an apostate from his Creator, not only did they neglect to punish it, but, in violation of all lawful order, they subjected and devoted themselves to it, as participators in the same apostasy. What can be imagined more dishonorable than this extreme depravity? Thus, I understand the name of the serpent, not allegorically, as some foolishly do, but in its genuine sense.
John Calvin on the Serpent