John Gill: Justification by the righteousness of Christ is the "essence of the Gospel"

John Gill on the importance of the doctrine of justification:

The doctrine of justification by the righteousness of Christ is a doctrine of great importance; the apostle speaks of it as if the essence of the gospel lay in it; and calls the opposite to it, justification by the works of the law, another gospel; (see Gal. 1:6,7; 3:8), it is a fundamental article of the gospel; some have called it, the "basis" of Christianity; it was the great doctrine of the reformation; what our first reformers made their chief study; and by it cut the sinews of "popery", the antichristian doctrines of penance and purgatory, of pardons and indulgences, of the merit of good works, works of supererogation, &c. Luther used to call it, "articulus stantis vel cedentis ecclesiae" the article of the church, by which it stands or falls; as this is, the church is; if this obtains, the church is in a well settled and prosperous state; but if this loses ground, and is rejected, it is in a ruinous one: if this is a rule to judge by, it may be easily discerned, in what case the church, and interest of religion, now are. This doctrine is the ground and foundation of all solid joy, peace, and comfort, in this life, and hope of eternal glory hereafter. (John Gill, A Body of Doctrinal Divinity: Book 6—Chapter 8: Of Justification)