Sin and forgiveness often confuse us because these two things are different even though the Bible does not specifically say so. One is on and the other is off, those are the two spheres of salvation.
As far as salvation is concerned, all sin is equal. James 2:10-11 says, "For whosoever shall keep all the law, and yet stumble in one point, he shall be guilty of the whole law. For he that said, Thou shalt not commit adultery, hath also said, Thou shalt not commit adultery. If you kill, then you have broken the law. Disobedience is the part of the law that exposes us to the transgression of the law. If we lie, we are not only liars but guilty of the whole law. Romans 6:23 says that the penalty for sin is death - any sin. It is an on or off, this or that situation. We are not guilty of transgressors. Every feeling and action that is motivated by selfishness or greed or anger is tantamount to cursing or condemning another. Fortunately, Jesus forgives every sin.
Yet God makes a distinction between sin. When Moses saw that the people of Israel had worshiped the golden calf, he said, "These people have sinned greatly" (Exodus 32:30). And Jesus' response to the adulterous woman (John 4:4-42; 8:1-11) was much different than Jesus' response to the Pharisees (Matthew 3:7; 12:34; 23; 33; Luke 3:7). He describes it in Matthew 23:23-24: "Woe to you, scribes and Pharisees, hypocrites, because you pay tithes of mint, myrrh, and cumin, and have forsaken the weightier matters of the law, judgment, mercy, and faith; but All these should be observed and the others should not be abandoned. You blind guides, you strain out the gnat, but swallow the camel."
We can also see a difference in how God allows us to experience our earthly and relational responses to sin. Lust for a friend's car can get you down in a relationship, but not as much as stealing that car. An angry feeling can be quickly forgotten, but killing hurts deeply.
God's recognition of this is seen in the law he gave to the Israelites. The various types of punishment for crimes depended on the extent of the injury and the stability of Israel as a society.
