Regeneration is a word derived from human birth. We must not understand this to refer only to giving birth itself, but it is inclusive of all that pertains to it, such as conception, fetal growth, and the birth itself. We must not be of the opinion that man possesses life prior to regeneration, as if there were a preparation for regeneration, which we would understand to be conversion. No, man is dead prior to regeneration and receives life by way of regeneration. There is no third state between death and life, and thus also not between being converted and unconverted.
Although we can make a distinction between calling, regeneration, conversion, and sanctification, considering them to be sequential—that is, the one issuing forth from the other—Scripture does not always use this distinction. Instead, Scripture comprehends all these in either one word or the other.
It is not the justice of God which requires regeneration, but it is a necessity as far as the will of God is concerned. Without satisfaction of the justice of God, absolutely no man can be saved. Regeneration, however, neither contributes anything toward satisfaction for guilt nor toward obtaining the right to eternal life. It would
therefore not be in conflict with His justice if it so pleased the Lord, at the moment of death, to translate a person who is chosen and reconciled through Christ’s death into the state of perfection and thus into eternal felicity. This is true for such children who die prior to birth or prior to the years of discretion. All the regenerate, whether they live a longer or shorter period and are converted at an earlier or later date, are made perfect in one moment at the hour of their death. However, it is the will and wisdom of God concerning those who have come to the years of discretion, not to bring them into heaven except He first regenerates them in this life by means of His Word.
Source: Wilhelmus à Brakel, The Christian's Reasonable Service, vol. 2, trans. Bartel Elshout (Morgan, PA: Soli Deo Gloria Publications, 1993), 233-34.