What is the highest blessing and privilege offered by the gospel? Many, if not most, people’s answer would involve something about forgiveness, salvation from the penalty of sin. In short, justification; and it is no wonder that most would answer in that way. Surely, it is a wonderful thing to be forgiven and freed from the threat of eternity in hell. But there is a greater blessing than that. Packer writes:

Adoption . . . is the highest privilege that the gospel offers: higher even than justification. This may cause raising of eyebrows, for justification is the gift of God on which since Luther evangelicals have laid the greatest stress, and we are accustomed to say, almost without thinking, that free justification is God’s supreme blessing to us sinners. Nonetheless, careful thought will show the truth of the statement we have just made.
   That justification—by which we mean God's forgiveness of the past together with his acceptance for the future—is the primary and fundamental blessing of the gospel is not in question. Justification is the primary blessing, because it meets our primary spiritual need. We all stand by nature under God’s judgment; his law condemns us; guilt gnaws at us, making us restless, miserable, and in our lucid moments afraid; we have no peace in ourselves because we have no peace with our Maker. So we need the forgiveness of our sins, and assurance of a restored relationship with God, more than we need anything else in the world; and this the gospel offers us before it offers us anything else. The first gospel sermons to be preached, those recorded in Acts, lead up to the promise of forgiveness of sins to all who repent and receive Jesus as their Savior and Lord (see Acts 2:38; 3:19; 10:43; 13:38--39; compare 5:31; 17:30--31; 20:21; 22:16; 26:18; Lk 24:47).
   In Romans, Paul’s fullest exposition of his gospel—“the clearest gospel of all,” to Luther's mind—justification through the cross of Christ is expounded first (chaps. 1—5), and made basic to everything else. Regularly Paul speaks of righteousness, remission of sins, and justification as the first and immediate consequence for us of Jesus' death (Rom 3:22-26; 2 Cor 5:18--21; Gal 3:13-14; Eph 1:7; and so on). And as justification is primary blessing, so it is the fundamental blessing, in the sense that everything else in our salvation assumes it, and rests on it—adoption included.
   But this is not to say that justification is the highest blessing of the gospel. Adoption is higher, because of the richer relationship with God that it involves. Some textbooks on Christian doctrine—Berkhof's, for instance—treat adoption as a mere subsection of justification, but this is inadequate. The two ideas are distinct, and adoption is the more exalted. Justification is a forensic idea, conceived in terms of law, and viewing God as judge. In justification, God declares of penitent believers that they are not, and never will be, liable to the death that their sins deserve, because Jesus Christ, their substitute and sacrifice, tasted death in their place on the cross.
   This free gift of acquittal and peace, won for us at the cost of Calvary, is wonderful enough, in all conscience—but justification does not of itself imply any intimate or deep relationship with God the judge. In idea, at any rate, you could have the reality of justification without any close fellowship with God resulting.
   But contrast this, now, with adoption. Adoption is a family idea, conceived in terms of love, and viewing God as father. In adoption, God takes us into his family and fellowship—he establishes us as his children and heirs. Closeness, affection and generosity are at the heart of the relationship. To be right with God the Judge is a great thing, but to be loved and cared for by God the Father is a greater.

—J. I. Packer, Knowing God (InterVarsity Press, 1993), 206–207