The serpent of Genesis is one of the most misunderstood figures in Genesis. Atheists occasionally point to this as proof the bible is at best an allegory. Some believers argue the serpent had a form different then what we know today changed by God’s curse; others believe it was simply a talking snake. There is an answer to the question though and it’s repeated in both the old and the New Testament.
The beginnings of understanding the identity of the serpent is, naturally, in Genesis. The serpent is described as the craftiest of animals (Genesis 3:1), and is cursed to have enmity with the woman (Genesis 3:15), and it is cursed to eat dust (Genesis 3:14). Also most obviously the serpent speaks to Eve (Genesis 3:1-5). This last characteristic is strange. The only other time an animal speaks in anywhere in the bible is a donkey directly given the ability by God (Numbers 22:28). The fact the Donkey only spoke when God opened its mouth makes it clear that something unusual is going on with the serpent. Also if it is merely a speaking animal its unusual Eve doesn’t seem surprised by this even though nothing before or after it suggests animals in the Garden could speak.
There is more in the book of Ezekiel (Ezekiel 28:11-17). On the simplest level this passage is discussing the King of Tyre but read the text itself. The says this King was in the Garden of Eden, as having precious stones as his covering and most tellingly as being a guardian cherub. Cherubim are referred to many times in scripture as angels (Ezekiel 10:7-8) as well as being present as guardians in the Garden of Eden (Genesis 3:24). It seems clear that the person being discussed in Ezekiel is more than just a simple mortal King (who himself was born long after man was cast out of Eden). Just as the Donkey was given speech by God the Bible is talking about a preternatural figure that was the power behind the throne of Tyre in this time.
Again this figure turns up in Isaiah (Isaiah 14:12-17). This time the passage is describing the King of Babylon but the text implies more is going on. This King is described as the Morning Star who fell from Heaven. It says he was going to be like God and exalt his throne above the stars but was cast down into Sheol. Like the being of Ezekiel this addresses not the moral King of Babylon but a spiritual force behind the throne.
The full identity of the serpent is most clearly revealed in the New Testament. Just as Isaiah describes Lucifer falling from Heaven, Jesus revealed he saw Satan fall (Luke 10:18). Saint Paul warns that just as Eve was deceived by the serpent he fears Christians may be deceived (2 Corinthians 11:3). The final nail though comes in Revelation. Revelation calls Satan the dragon and the SERPENT of old (Revelation 12:7-9). More than any other verse this passage spells out in clear language that the lying serpent of Genesis is not simply a snake but the Devil himself leading to the first temptation of man.
Multiple translations of Scripture: http://www.biblegateway.com/