Curse of the Law

Things That Differ writes:The principle of law or justice, for example, has continued unchanged through
the ages. No matter what the dispensation, when wrong is done God's sense of
justice is offended. This may be simply demonstrated by three Scriptural examples:
Cain lived before the dispensation of the law by Moses. Cain murdered his
brother Abel. Was this right or wrong? Did he get into trouble over it?( He did, although the written law had not yet been given.)
Davidlived under the law of Moses. He also committed murder. Was this
right or wrong? (Wrong, of course, and he also got into trouble over it.)
You and I live after the law, under the dispensation of grace. Suppose we
should commit murder, would that be right or wrong? Would we get into trouble
over it with God ? Would the fact that Christ bore our sins on Calvary, make
murder any more right? Would God look upon it as less sinful because it took
place under the dispensation of grace?You say, in the case of the true believer today, the full legal penalty
for the sin would still have been borne by Christ and, though he knew it not, David too
was forgiven on this ground. But does not the very fact that David's sins and ours were
paid for rather than overlooked, prove that the principles of law and justice remain fixed?