“…indeed none can receive Christ and reject his doctrine; but, in receiving Christ, must first receive his doctrine, and so Christ therein: and so he that receiveth Christ is said to believe the gospel, and every true receiver of Christ is a receiver of his doctrine, because that is the seed by which he is conceived and born, and it is the milk by which he is brought up and nourished to eternal life, 1 Pet. i. 23; chap. ii. 2. I need not here stand to commend the gospel doctrine; it is enough to say that, by the Lord’s blessing upon it, it is the seed to conceive and the milk to nourish all the children of God. Why? it is the channel in which the Spirit runs; “Received ye the Spirit by the works of the law, or by the hearing of faith?” Gal. iii. 2. It is the organ of the almighty power of God; “I am not ashamed of the gospel of Christ, for it is the power of God to salvation, to every one that believeth;”
His power in working faith, his power in measuring faith, and his power in saving sinners in a way of believing, is put forth in the gospel; Why? “For therein is the righteousness of God revealed from faith to faith,” Rom. i 16, 17. The law hath convinced many, but never converted one to this day; and a gospel minister may preach the law for many good ends, but it is the gospel part of preaching that doth the business, if the power of God be going along with is; for the gospel is the only channel wherein the converting power of the Spirit runs; “Faith comes by hearing, and hearing by the word of God:” Christ is revealed therein in order to his being received.”
Ralph Erskine, “Gospel-Principle, the Foundation of Gospel Practice; or, The Great Duty of Receiving Christ, and Walking in Him, Opened,” The Works of Ralph Erskine, vol. 4, pp. 181-182.