Thomas Boston, Works, 3:377:
The doctrines of the gospel believed with the heart, teach us that, denying ungodliness and worldly lusts, we should live soberly, righteously, and godly in the present world. As Christ is the end of the law, so I may say, the law is the end of the gospel; for it is the great design of the gospel revelation, to bring back sinners to that righteousness and holiness which the law requires. The gospel never gains its end among a people, till a strain of piety and holiness run through their whole lives.
Source: http://www.puritanboard.com/f25/law-end-gospel-83880/, Comment #1 (Thank You, Reverend Winzer!)