While on Earth. The law of Moses brings wrath. An eye for an eye - When you hit someone you expect to get hit back.
Mercy stops action reaction.
Love covers all sin. And suddenly, when they had looked round about, they saw no man any more, save Jesus only with themselves. The gospel is the words of Jesus Christ while on earth. The gospel in the New Testament is the Christ-message, not the books which were written to spread the message. Much more then, being now justified by his blood, we shall be saved from wrath through him.