George Eldon Ladd, A Theology of the New Testament (Eerdmans, 1993), pages 483–484:
Justification, which primarily means acquittal at the final judgment, has already taken place in the present. The eschatological judgment is no longer alone future; it has become a verdict in history. Justification, which belongs to the Age to Come and issues in the future salvation, has become a present reality inasmuch as the Age to Come has reached back into the present evil age to bring its soteric blessings to human beings. An essential element in the salvation of the future age is the divine acquittal and the pronouncement of righteousness; this acquittal, justification, which consists of the divine absolution of sin, has already been effected by the death of Christ and may be received by faith here and now. The future judgment has thus become essentially a present experience. God in Christ has acquitted the believer; therefore he or she is certain of deliverance from the wrath of God (Rom. 5:9) and no longer stands under condemnation (Rom. 8:1). …
Justification is one of the blessings of the inbreaking of the new age into the old. In Christ the future has become present; the eschatological judgment has in effect already taken place in history. As the eschatological Kingdom of God is present in history in the Synoptics, as the eschatological eternal life is present in Christ in John, as the eschatological resurrection has already begun in Jesus’ resurrection, as the eschatological Spirit is given to the church in Acts (and in Paul), so the eschatological judgment has already occurred in principle in Christ, and God has acquitted his people.
(HT: Tony Reinke)