God said: I'm going to solve that problem. I'm not going to make a covenant with man anymore. I'm going to send My Son - I'm going to put the spirit of My Son in them - and then I'm going to make a covenant with Myself!
Since He could swear by no greater - He swore by Himself. So now your covenant with God is as secure as the spirit within you - because He gets the Justice; and you get the Mercy.
Your job is to: continually respond; continually have faith; continually move into the life that's provided to you in Jesus Christ!