"What? know ye not that your body is the temple of the Holy Spirit which is in you, which ye have of God, and ye are not your own? For ye are bought with a price: therefore glorify God in your body, and in your spirit, which are God's" (1 Cor.6:19-20).
Once a person believes the gospel he is no longer his own because he is bought by God with the precious blood of Christ. Since that price is so costly God will not lose that which He purchased.