It is at the heart of one of the great plagues of evangelicalism-the unconverted church member. Moreover, this matter relates directly to Christian parents who long for the conversion of their children.
Regeneration is the new birth, sanctification is the growth that necessarily results from it.
Justification is God's declaration that a believing sinner is righteous because of the merits of Christ imputed to him. Sanctification is the believer leaving the courtroom where God has once and for all time declared him righteous, and immediately beginning the process whereby God's Spirit enables him to increasingly conform to Christ's righteousness, both inwardly and outwardly. Tis as much the nature of one that is spiritually new born, to thirst after growth in holiness, as 'tis the nature of a newborn babe, to thirst after the mother's breast. The process is progressive, but is never completed in this life. Sanctification is ultimately fulfilled in glorification.