From the puritan pastor Ralph Venning:
God is holy, without spot or blemish, or any such thing, without any wrinkle, or anything like it, as they also that are in Christ shall one day be (Ephesians 5.27). He is so holy, that he cannot sin himself, nor be the cause or author of sin in another. He does not command sin to be committed, for to do so would be to cross his nature and will. Nor does he approve of any man’s sin, when it is committed, but hates it with a perfect hatred. He is without iniquity, and of purer eyes than to behold (i.e. approve) iniquity (Habakkuk 1:13).
On the contrary, as God is holy, all holy, only holy, altogether holy, and always holy, so sin is sinful, all sinful, only sinful, altogether sinful, and always sinful (Genesis 6.5). In my flesh, there dwelleth no good thing (Romans 7.18). As in God there is no evil, so in sin there is no good. God is the chiefest of goods and sin is the chiefest of evils. As no good can be compared with God for goodness, so no evil can be compared with sin for evil.
In short, sin is the dare of God’s justice, the rape of his mercy, the jeer of his patience, the slight of his power, the contempt of his love, as one writer prettily expresses this ugly thing. We may go on and say, it is the upbraiding of his providence (Psalm 50), the scoff of his promise (2 Peter 3.3-4), the reproach of his wisdom (Isaiah 29.16).
You can read his complete treatise on the sinfulness of sin here.