What was the spiritual preparation for the sacrament of baptism?

The preparation of those seeking baptism is not limited to listening to teachings, memorizing the creed, and reciting some prayers. Tertullian says, “They who are about to enter baptism ought to pray with repeated prayers, fasts, and bendings of the knee, and vigils all the night through, and with the confession of all by-gone sins.”¹³²⁶ The Apostolic Constitutions also state: “he who is to be initiated into [Christ’s] death ought first to fast, and then to be baptized.”¹³²⁷ St. Cyril the Great says, “Prepare your hearts to accept the teachings in order to partake of the eternal heavenly sacraments. Pray with more perseverance for God to make you worthy of the eternal holy sacraments. Pray without ceasing day and night, and when you lose sleep from your eyes, free your mind to pray. If any sinful thought gets into you, turn your mind to meditate on the judgment, and then you will remember salvation. Offer all your minds to study so that you may despise the despicable matters.”

1324 Constitutions of the Holy Apostles 7.3.39 (ANF 7:475–476).

1325 St. Ambrose of Milan, Letter 20 (NPNF II/10:423).

1326 Tertullian, On Baptism 20 (ANF 3:678).

1327 Constitutions of the Holy Apostles 7.2.22 (ANF 7:469).

The Rites of Holy Baptism