For the kingdom of God,.... By "the kingdom of God" is not meant the kingdom of heaven, or the ultimate glory and happiness of the saints; though that is a kingdom prepared by God, which he gives to his children, calls them to by his grace, and will give them an abundant entrance into, when time shall be no more with them; and though that is not attained to "in", or "by word", by mere talk and profession; not everyone that says Lord, Lord, shall enter into it; or that professes the name of Christ, and prophesies in it; but "in" or "by power"; through the power of God, beginning, carrying on, and finishing a work of grace upon the soul, and keeping it, through faith, unto salvation: nor the kingdom of grace, or that internal principle of grace in the soul, which reigns, and by which Christ reigns there, and by which the saints appear to be kings as well as priests unto God: though this also does not lie "in word", in a profession of faith, in talking about love, and in making pretensions to the knowledge of divine things; nor merely in deeds, and outward actions, in bodily exercise, in a form of godliness, and a round of religion, and a show of righteousness;but in power: in internal powerful godliness; for true godliness is a powerful thing; faith is powerful, and so is love; and so is prayer, and preaching; and so is all religion, internal and external, where there is the life and truth of grace, and that in exercise.
But I rather think the Gospel is here meant, often in Scripture called the kingdom of God, and the doctrines of it, the mysteries of the kingdom; because it is a message from the King of kings; the means of setting up the kingdom or grace in the heart; its subjects are things concerning the kingdom of God; it is what has brought life and immortality, or an immortal life to light; and gives the best account of the invisible glories of the heavenly state, and points out the saints' meetness for it, and title to it; declaring that except a man is born again, and has a better righteousness than his own, even that of Christ's, he shall neither see nor enter into the kingdom of heaven.