How is it possible to say that the serpent, created by God dumb and irrational, was endowed with reason and speech? For if it had the power of itself to speak, to discern, to understand, and to reply to what was spoken by the woman, there would have been nothing to prevent every serpent from doing this also. If, however, they say again that it was according to the divine will and dispensation that this [serpent] spoke with a human voice to Eve, they render God the author of sin.
Neither was it possible for the evil demon to impart speech to a speechless nature, and thus from that which is not to produce that which is; for if that were the case, he never would have ceased (with the view of leading men astray) from conferring with and deceiving them by means of serpents, and beasts, and birds. From what quarter, too, did it, being a beast, obtain information regarding the injunction of God to the man given to him alone, and in secret, not even the woman herself being aware of it?
Why also did it not prefer to make its attack upon the man instead of the woman? And if you say that it attacked her as being the weaker of the two, [I reply that], on the contrary, she was the stronger, since she appears to have been the helper of the man in the transgression of the commandment. For she did by herself alone resist the serpent, and it was after holding out for a while and making opposition that she ate of the tree, being circumvented by craft; whereas Adam, making no fight whatever, nor refusal, partook of the fruit handed to him by the woman, which is an indication of the utmost imbecility and effeminacy of mind.
And the woman indeed, having been vanquished in the contest by a demon, is deserving of pardon; but Adam shall deserve none, for he was worsted by a woman—he who, in his own person, had received the command from God. But the woman, having heard of the command from Adam, treated it with contempt, either because she deemed it unworthy of God to speak by means of it, or because she had her doubts, perhaps even held the opinion that the command was given to her by Adam of his own accord.
The serpent found her working alone, so that he was enabled to confer with her apart. Observing her then either eating or not eating from the trees, he put before her the fruit of the [forbidden] tree. And if he saw her eating, it is manifest that she was partaker of a body subject to corruption. “For everything going in at the mouth, is cast out into the draught.” If then corruptible, it is obvious that she was also mortal. But if mortal, then there was certainly no curse; nor was that a [condemnatory] sentence, when the voice of God spoke to the man, “For earth you are, and unto earth shall you return,” as the true course of things proceeds [now and always].
Then again, if the serpent observed the woman not eating, how did he induce her to eat who never had eaten? And who pointed out to this accursed man-slaying serpent that the sentence of death pronounced against them by God would not take [immediate] effect, when He said, “For in the day that you eat thereof, you shall surely die?” And not this merely, but that along with the impunity [attending their sin] the eyes of those should be opened who had not seen until then? But with the opening [of their eyes] referred to, they made entrance upon the path of death.
Source: Fragments from the Lost Writings of Irenaeus (New Advent)