“But your iniquities have separated you from God;
and you sins have hidden his face from you, so that He will not hear.”
Isaiah 59:2 

God is holy, perfect in every way. Sin is an abomination to Him. It is the manifestation of evil, outright rebellion and disobedience displayed against God. We sin because we are sinners.

When Adam and Eve sinned, they died spiritually. Prior to there sin, they enjoyed continual fellowship with God. But when they sinned in the garden, they were immediately separated from God. No longer did they enjoy the close fellowship with the Lord. There sin served as a barrier between them and a holy God.