Anselm of Canterbury(1033-1109); from Cur deus homo?

Book I

xi. The problem is, how can God forgive man’s sin? To clear our thoughts let us first consider what sin is, and what satisfaction for sin is. …To sin is to fail to God His due. What is due to God? Righteousness, or rectitude of will. He who fails to render this honour to God, robs God of that which belongs…