Chapter 16 — Part II: The Sacraments — Baptism
Section 120. This certainly they cannot do without sacrilege and without incurring what theologians call an irregularity. According to the authority of Pope Alexander the conditional form of Baptism is to be used only when after due inquiry doubts are entertained as to the validity of the previous Baptism. In no other case is it ever lawful to administer Baptism a second time, even conditionally.