As an indispensable means to participation in salvation and as a condition of reception into the communion of the church, baptism was practised from the earliest times. Infant baptism, though not universally adopted, was yet in theory almost universally admitted to be proper. Tertullian alone is found opposing it. All adults who desired baptism had, as Catechumens, to pass through a course of training under a Christian teacher. Many, however, voluntarily and purposely postponed their baptism, frequently even to a deathbed, in order that all the sins of their lives might be certainly removed by baptismal grace. After a full course of instruction had been passed through, the Catechumens prepared themselves for baptism by prayer and fasting, and before the administration of the sacred ordinance they were required to renounce the devil and all his works (_Abrenuntiare diabolo et pompæ et angelis ejus_) and to recite a confession of their faith. The controversy as to whether baptism administered by heretics should be regarded as valid was conducted with great bitterness during the 3rd century. § 35.1. =The Preparation for Receiving Baptism.=--After a complete exposition of the evangelical moral code in chap. 1-6, the _Teaching of the XII. Apostles_ proceeds thus: Ταῦτα πάντα προειπόντες βαπτίσατε εἰς τὸ ὄνομα, etc. At this time, therefore, besides the necessarily presupposed acquaintance with the chief points in the gospel history, the initiation into the moral doctrine of the gospel of the person receiving baptism was regarded as most essential in the baptismal instruction. In this passage there is no mention of a doctrinal course of teaching based upon a symbol. But what here is still wanting is given in a summary way in chaps. 7 ff. in the instructions about baptism and the Lord’s supper attached to the baptismal formula and the eucharistic prayers. This therefore was reserved for that worship from which the candidates for baptism and the newly baptized had to gather their faith and hope as to the future completion of the kingdom of God. First the struggle against Gnosticism obliged the church to put more to the front the doctrines of faith which were thereby more fully developed, and to concern itself with these questions even in the instruction of the Catechumens. The custom, which the Didache and Justin Martyr show to have been prevalent in post-Apostolic times, of the baptiser together with others voluntarily offering themselves taking part with the candidate for baptism in completing the preparation for the holy ordinance by observing a two days’ fast, seems soon, so far as the baptiser and the others were concerned, to have fallen into desuetude, and is never again mentioned.--Since the development of the Old Catholic church the preparation of candidates for baptism has been divided into two portions of very unequal duration,