While the Lord's Supper should be used frequently by the believer, 1 Cor. 11, 26, Scripture nowhere commands that Baptism should be applied to one and the same person oftener than once. On the contrary, Baptism, once applied, should comfort and exhort the believer throughout his life, 1 Pet. 3, 21; Gal. 3, 26. 27; Rom. 6, 3ff. For this reason the apostles in the New Testament again and again remind Christians of their Baptism, 1 Cor. 1, 13; 6, 11; 12, 13; Rom. 6, 3 ff.; Eph. 4, 5; Col. 2, 11. 12; Titus 3, 5. 6; 1 Pet. 3, 21; etc., and urge them to heed not only its sweet comfort, but also its great significance for sanctification. Baptismus semper exercendus est. Large Catechism, De Baptismo, 65.
The daily repentance of the Christian believer (poenitentia stantium) is nothing else than a constant penitent return to the covenant of grace which God has established with him in Baptism, or the continuous apprehension by faith of the gracious promises of forgiveness, life, and salvation offered and conveyed to him in this precious Sacrament. So also the repentance of the apostates from the Christian faith (poenitentia lapsorum) is only a return to their baptism (reditus ad baptismum), not their laying hold of the "second board" (secunda tabula) of the papistic penance (satisfactio operis). This truth the Christian minister must always inculcate upon his hearers, especially when he is called upon to instruct and confirm catechumens.
Confirmation is not "a confirmation of Baptism" nor "a Sacrament which supplements and perfects Baptism," but only a public profession of loyalty to the true God, who in Baptism establishes His covenant of grace with men. It is the believer's public reply to his baptism, or his public confession of Christ, who has cleansed him in Baptism, Eph. 5, 26; Matt. 10, 32. Confirmation, of course, was not instituted by Christ; yet we retain it as a laudable, useful Christian custom (though not as a Sacrament), because it so vividly reminds the believer of His baptism and the exceeding grace which God conferred on him in that priceless Sacrament.