Last year I wrote that we should speak of regeneration as something that God progressively-continually accomplishes in us, and cited Calvin as saying that regeneration is something that occurs progressively.
Ian Hewitson makes a similar observation:
After a brief treatment of union with Christ in chapter 1 [of the Institutes, book 3], Calvin speaks of regeneration. Under the rubric of regeneration, Calvin was taking up the topic of sanctification. (At that point of theological development, “regeneration” had the broad significance of what we now understand by “sanctification”). Calvin, having completed that topic, then takes up the topic of justification. The polemic involved for Calvin was to demonstrate that the Protestant conception of justification did not militate against the moral integrity of the believer as Roman Catholic theology believed would inevitably be the case if a doctrine of justification was grounded in imputed righteousness. Calvin refutes such an understanding by taking up sanctification first, without calling into question the doctrine of justification as a forensic category grounded in the imputation of the righteousness of Jesus Christ. Although the Westminster Confession of Faith (in chapter XIII) sees regeneration as the beginning of sanctification, I am not aware of any modern Reformed theologian who takes up the topic of sanctification before the topic of justification according to the same pattern as the Confession. Reformed theologians do take up the topic of regeneration, and regeneration is a category of transformation. In the course of theological development, the conception of regeneration was narrowed down to initial transformation that is wrought at the inception of the process of sanctification. In this way, regeneration is thought of as a transforming “act” of God that accounts for the emergence of faith in the believer. Attention is then turned to other “acts” of God that precede the “process” of sanctification. The movement is from regeneration to justification. Regeneration gives rise to the faith that justifies and precedes sanctification. Such a pattern is within the bounds of Reformed theology and not contrary to Calvin’s approach, but it remains the case that it is not the pattern found in Book III of the Institutes. (Trust and Obey, 25-26)