Take heed, brethren, lest there be in any of you an evil heart of unbelief, in departing from the living God.
Hebrews 3:12 (KJV)
Unbelief is evil in the sight of God because unbelief is the root cause for every sin. Yet simply believing God through placing our faith in Jesus makes us one hundred percent righteous in the eyes of God. Just as unbelief produces sin, so will believing that Jesus is enough to make us righteous actually produce right living, victory over sin, and deliverance from sickness, poverty and bondage in our lives.