Therefore, just as through one man sin entered the world, and death through sin, and thus death spread to all men, because all sinned (ROMANS 5:12)
Sin actually entered the world through one man—Adam. Adam was God’s special creation, the very first man. When Adam was created on Day Six, God said that he was to rule over all the earth and all that was on it. God also clearly told Adam not to eat of the fruit of the tree and if he ate he would surely die. Adam was the one who was given the instruction to obey what God said. So, because Adam was told to obey, and Adam chose to disobey God and eat the fruit, and Adam was given dominion to rule over the earth, Adam gets the blame for sin. Sin entered the world—to all of us—through Adam because we are his descendants.
So, what about Satan? He was not the father of the human race (it was Adam), he had not been given dominion over all the earth (that was Adam, too), and so he is not the one responsible for sin in our world today. Adam’s sin is considered the first sin . . . his is the sin that brought judgment on the human race and, in fact, on the entire creation. It is also important to understand that there is no way for Satan or fallen angels to have salvation. They have already been judged and thrown from heaven. Humans can have their sins forgiven. Therefore, the way God deals with humans is different from the way He deals with the angels.