The whole Old Covenant was meant to teach the lesson of the absolute and indispensable necessity of obedience for a life in God's favour. The New Covenant comes, not to provide a substitute for that obedience in faith, but through faith to secure the obedience, by giving a heart that delights in it and has the power for it. And men abuse the free grace, that without our own obedience accepts us for a life of new obedience, when they rest content with the grace, without the obedience it is meant for. They boast of the higher privileges of the New Covenant, while its chief blessing, the power of a holy life, a heart delighting in God's law, and a life in which God causes and enables us, by his indwelling Spirit, to keep His commandments, is neglected. If there is one thing we need to know well, it is the place obedience takes in the New Covenant.
Obedience is essential.
At the very root of the relation of a creature to his God, and of God admitting the creature to His fellowship, lies the thought of obedience. In the promise of the New Covenant it takes the first place. The crowning gift of Christ's exaltation was the Holy Ghost, to bring salvation to us as an inward thing. The first Covenant demanded obedience, and failed because it could not find it. The New Covenant was expressly made to provide for obedience.