The Book of Life was written (finished, done, and populated) from the foundation of the world. Which means every person that was named there was named and had his name on there from the foundation of the world. It follows therefore that the blood shed FROM THE FOUNDATION of the world by the Lamb slain FROM THE FOUNDATION OF THE WORLD had their redemption and salvation redeemed IN GOD'S ETERNAL MIND before He even had the first star created.
These are the elect who at that point were not even existing in time, on earth, but in God's mind, whose salvation and redemption as far as the Triune God is concerned, is done and delivered.
Their eternal salvation and redemption, authored by Christ, was PASSIVE, ENTIRELY BASED ON GOD'S MERCY AND GRACE, and TOTALLY UNRELATED TO THEIR SOCIAL, RACIAL, TRIBAL, NATIONAL, THEOLOGICAL, CREDAL, SOTERIOLOGICAL statuses IN TIME.
Their salvation is UNTO HEAVEN, sealed on earth, by the blood of the Lamb of glory slain at the cross on Calvary.
Now, Christ having finished what He was supposed to do here on earth, in time, for the eternal benefit of the elect, directed His apostles (not His church as many maintain), to go out and preach the good news of a God who condescended to man in human form, and took their sins away through His blood, and to instruct those whom they (in their limited physical capacity) are able to reach, in the way they are to live with each other, and those without, as pilgrims on their way to their true country.