Hallelujah !Because in the Purpose of God Christ was slain for the sins of those whose names had been written in the Lambs Book of Life Rev 13:8228
And all that dwell upon the earth shall worship him, whose names are not written in the book of life of the Lamb slain from the foundation of the world.
Christ had been pre-appointed to be slain 1 Pet 1:20
20 was foreordained before the foundation of the world, but was manifest in these last times for you,
Hence, all the Chosen of God were Justified in Christ from the time of Christ's appointment to be their redeemer, He became their Surety, so that no sin of theirs would be charged to their account, but to His, and that's why He came on the earth, by Divine Appointment ! And this Justification is that Justification of Life Rom 5:18 because they're names are written in the Book of Life !