In the world of Christian legalism, justification may be presented as a free gift, but sanctification is often taught to be a progressive process that we must work at in order to possess or experience. This misunderstanding of what was accomplished for us through the work of the cross will eventually lead people back into a mentality of works and guilt, or self-righteousness and boasting in themselves. Jesus has (already) become our sanctification, and it cannot be defined outside of what he did on our behalf.
The word "sanctified" means "set apart," "purified," "made holy." Sanctification is a matter of being set apart to God, by His gift, by grace through faith. This is a finished work. All believers are heaven-ready right now at this very moment, because they have been sanctified once and for all!