Regeneration has to do with our spiritual life within [a God wrought change of hearts of stone]. Justification has to do with our standing before God’s law [right legal standing – declared right before God]. But adoption has to do with our relationship with God as our Father, and in adoption we are given many of the greatest blessings that we will know for all eternity. When we begin to realize the excellence of these blessings , and when we appreciate that God has no obligation to give us any of them, then we will be able to exclaim with the apostle John,
“See what love the Father has given us, that we should be called children of God; and so we are” (1 John 3: 1).
Grudem, Wayne (2009-05-18). Systematic Theology: An Introduction to Biblical Doctrine (p. 739). Zondervan. Kindle Edition. [lightly edited for application]