Even though the term adoption occurs only five times in Scripture (all in Paul's epistles), its "marking" function within redemptive-history demonstrates its theological significance. Vertical adoption (i.e., God adopting us as His children) plays a key role from the beginning of the unfolding story of redemption (before god even created the world) all the way to the end (when all God's adopted children enjoy the full privileges of their adoption in the new heaven and new earth).
In Ephesians 1:5, Paul states that God predestined us to adoption in eternity past. In Romans 9:4, we learn that our adoption was foreshadowed in God's adoption of Israel as His firstborn son.
Galatians 4:4-6 teaches that "when the fullness of time had come" God sent His Son to redeem us so that we might receive adoption as sons. Adoption was the penultimate objective at the climax of redemptive-history.
In Romans 8:15-16, Paul speaks of our present experience as God's sons by adoption, while in Romans 8:23, he points forward to its consummation in the glorification of our bodies. Clearly, adoption possesses unique importance from the pre-temporal beginning of the unfolding story of redemption all the way to redemptive-history's consummation. T4A is committed to helping Christians understand the redemptive-historical significance of God's work in adoption.