I am excited about the Justinian Code being online. Check out the following laws and commentary and see how seriously re-baptism was taken by the Church. And then think about how trivial rebaptism is in our day where people get baptized 2,3 or multiple times since we have lost the wicket on what the teaching of the Church is on the matter.
That the Holy Baptism be not Repeated.
(Ne sanctum baptisma iteretur).
1.6.1. Emperors Valens, Gratian and Valentinian to Florianus, Vicar of Asia.
We deem unworthy of the priesthood the priest who unlawfully repeats the holy rite of baptism. For we condemn the error of those who, despising the precepts of the apostles, by rebaptising those who have already received the Christian sacraments, do not purify them but defile and pollute them under pretense of cleaning them.
Given at Constantinople October 17 (377).
See C. Th. 184.108.40.206.
Note. Baptism was believed to purify the recipient from guilt of previous sin. The Donatists held that this sacrament administered by polluted hands was inefficacious. Hence when anyone was received into their fold, they rebaptized him though already baptized by the priests of the orthodox church. The Eunomians and Novations, too, rebaptized converts to their faith. This was considered sacrilegious. Boyd, The Ecc.
Edicts of the Theod. Code 61, 62. Gothofredus on C. Th., 16.6.
1.6.2. Emperor Honorius and Theodosius to Anthemius, Praetorian Prefect.
If any person shall be discovered to rebaptize anyone imbued with the mysteries of the Catholic faith, he, together with him who has permitted this infamous crime provided the person persuaded to be rebaptized be of an age capable of crime shall be punished by death.
C. Th. 16.6.6.
1.6.3. Emperors Theodosius and Valentinian to Florentius, Praetorian Prefect.
No heretic must be permitted to rebaptize, either free persons or their own slaves who have been initiated into the mysteries of the orthodox, nor forbid those (slaves) whom he has bought or whom he has in any manner, and who have not yet joined his superstition, to adhere to the religion of the Catholic Church.
1. If anyone does so, or if a free man permits himself to be rebaptized, or if asks to repeat it, he shall be condemned to a fine of ten pounds of gold. Neither of them shall have power to make a testament or a gift.