Sin is the breaking of God’s law (i.e. lawlessness) (1 John 3:4). If God says “Do not lie” and you lie, then you have broken His law and sinned. Sin separates us from God (Isaiah 59:2). All human beings have sinned and, “the wages of sin is death…” (Romans 6:23). So, to sin, to break God’s law, results in judgment. If God did not judge the sinner, then He is not upholding His holiness and he would be allowing sinners to go unpunished.