This "everlasting righteousness" comes to us through believing. We are "justified by faith" (Rom. 5:1), the fruit of which is "peace with God through our Lord Jesus Christ."
It is of this "everlasting righteousness" that the Apostle Peter speaks when he begins his second epistle thus: "Simon Peter, a servant and an apostle of Jesus Christ, to them that have obtained like precious faith with us, through the righteousness of God and our Saviour Jesus Christ" (II Pet. 1:1).
This righteousness is "reckoned" or "imputed" to all who believe, so that they are treated by God as if it were actually theirs. They are entitled to claim all that which such a righteousness can merit from God as the Judge of righteous claims. IT DOES NOT BECOME OURS GRADUALLY, or in fragments or drops; but IT IS TRANSFERRED TO US ALL AT ONCE. It is not that so much of it is reckoned to us (so much to our account, as men in business say) in proportion to the strength ofour faith, or the warmth of our love, or the fervor of our prayers; but the whole of it passes over to us by IMPUTATION; we are "accepted in the Beloved" (Eph. 1:6); we are "complete in him, who is the head of all principality and power" (Col. 2:10). In its whole quality and quantity, it is transferred to us. Its perfection represents us before God; its preciousness, with all that that preciousness can purchase for us, henceforth belongs to us (I Pet. 1:7).
This is God's way of lifting man out of the horrible pit and the miry clay, of giving him a standing and a privilege and a hope far beyond that which mere pardon gives and no less far above that which first Adam lost. To be righteous according to the righteousness of the first Adam would have been much; but to be righteous according to the righteousness of the last Adam, the Lord from heaven, is unspeakably and inconceivably more. "It is God that justifies," and He does so by imputing to us a righteousness which warrants Him as the Judge to justify the unrighteous freely.