Evil in the Old Testament is not personified as it is in the New Testament. Depending on your interpretation of the Hebrew word for Satan, meaning adversary, the term is more often a designation than a proper name in the Old Testament.
The Apostle Paul associates the serpent in Genesis 3 with a personified devil: “But I’m afraid that your minds might be seduced in the same way as the snake deceived Eve with his devious tricks. You might be unable to focus completely on a genuine and innocent commitment to Christ” (2 Corinthians 11:3, CEB).
The Apostle John clearly delineates the Tempter in the Garden of Eden as Satan or the devil: “So the great dragon was thrown down. The old snake, who is called the devil and Satan, the deceiver of the whole world, was thrown down to the earth; and his angels were thrown down with him” (Revelation 12:9, CEB). The word “old” here refers to the fact that Satan’s appearance on Earth was at an early stage of the world’s history and has long been occupied with the task of deceiving and opposing God’s elect.