At Mike Ratliff’s blog, Possessing the Treasure, he writes:
God is Holy. However, at the fall (Genesis 3) Man fell into sin. This fall corrupted all of Adam’s line so that each is born with a sin nature and completely separate from God. Why? God is Holy and is completely separate from all that is not. Christians are not separate from God because, at their salvation, they are forgiven and declared righteous by God because of the redemptive work of Christ on the Cross. The Lord Jesus Christ paid heavily to accomplish the atonement for the sins of those for whom He died.
I always like to link to Mike’s resources, as they are usually rich in Biblical truth. I’d suggest reading this post as well. The rest of it can be found here.