As ye will not be libertines in your life and practice, being dead to sin and the world with Christ; so ye will not be legalists in your life and practice neither, being also dead with him to the law as a covenant of works. Your obedience will run in another channel than it did before your union with Christ, even in the channel of the gospel. Ye will serve in newness of spirit, in faith and love. The frowns of a merciful Father will be a terror to you to frighten you from sin; love and gratitude will prompt you to obedience. The grieving of the Spirit of a Saviour will be a spring of sorrow to you; and his atoning blood and perfect righteousness will be the spring-head of all your comfort before the Lord; your good works but streams thereof, as they evidence your saving interest in these, are accepted through them, and glorify God your Saviour.
Ye will not continue to serve in the oldness of the letter, as before; at what time the law was the spring of all the obedience ye performed; fear of the punishment of hell for your sins, and hope of the reward of heaven’s happiness for your duties, being the weights that made you go, though for all them you often stopped; your sorrows springing from your ill works, under the influence of the law allenarly; and your comforts from your good works, under the same influence; ye being alive to the law and dead to Christ. Romans vii. 6, “But now we are delivered from the law, that being dead wherein we were held; that we should serve in newness of spirit, and not in the oldness of the letter.” If by faith you wholly rely on Christ’s righteousness, the holiness of his nature, the righteousness of his life, and his satisfaction for sin, how is it possible but ye must be dead to the law? for "the law is not of faith" Galatians iii. 12. But if you perform your obedience for life and salvation, looking for acceptance with God on the account of your works, you go in a way directly opposite to the way of faith, and either altogether reject Christ’s satisfying of the law, or else impute imperfection unto his payment of the bond. And “Christ is become of no effect unto you, whosoever of you are justified by the law; ye are fallen from grace,” Galatians v. 4.
—Thomas Boston(1676-1732) “A View of the Covenant of Grace”