I am living in a vile, wretched, sinful, fleshly body. I only understand what God enables me to understand by His Holy Spirit.
What I wrote in that sentence is taught in God's Word.
Christ is the Surety of God's elect, their sins were imputed to Him and He paid their sin debt at the cross.
"When, I say, the elect of God are justified from eternity, I do not think, that they had an actual personal existence from eternity, though they had a representative one in Christ; or that an actual payment of their debts, or an actual satisfaction for their sins was then made by Christ, though he engaged to do it; nor do I intend justification from eternity, in such a sense, as to set aside the imputation of Adam's sin to the condemnation of the elect in him; or to render Christ's bringing in an actual righteousness in time unnecessary; or to make faith useless in our justification, in our own consciences, as, I hope, I shall shortly make appear; yet, on the other hand, I mean more by justification from eternity, than merely God's prescience, or foreknowledge of it, to whom all works are known, from the beginning of the world, from eternity; (Acts of the Apostles 15:18) more than a mere resolution and purpose to justify his elect in time, he calling things that are not, as though they were; (Romans 4:17) or, in other words, more than a decretive justification, as some divines call it; who apprehend that God's elect can, in no other sense, be said to he justified from eternity, than they may be said to he sanctified or glorified from eternity, because he had decreed to sanctify and glorify them: I say, I mean more than thus, and assert, with Dr. Ames, that justification "is a sentence conceived in the mind of God, by the decree of justification;" that this is an act in God, all whose acts in him are eternal; that this is the grand original sentence of justification; of which that pronounced on Christ, as our representative, when he rose from the dead, and that which is pronounced by the Spirit of God in the conscience of believers, as well as that which will be pronounced before men and angels, at the general judgment, are no other than so many repetitions, or renewed declarations; that this includes the whole complete esse of justification; being, as Mr. Rutherfoord observes, "An eternal and immanent act in God, and not transient upon an external subject. Of which sort, adds he, are the acts of election and reprobation, which have their whole complete being before the persons elected, reprobated, or justified, either begin to be, live or believe, or do any thing good or evil." In a word, I apprehend, that as God's eternal decree of election of persons to everlasting life, is the eternal election of them, so God's will, decree, or purpose, to justify his elect, is the eternal justification of them; though his eternal will to sanctify them is not an eternal sanctification of them; because sanctification is a work of God's grace upon us, and within us, and so requires our personal existence. Justification is an act of God's grace towards us, is wholly without us, entirely resides in the divine mind, and lies in his estimation, accounting and constituting us righteous, through the righteousness of his Son; and so required neither the actual existence of Christ's righteousness, nor of our persons, but only that both should certainly exist in time."
- excerpt from John Gill's "The Doctrine Of Justification, By The Righteousness Of Christ, Stated And Maintained"