This is an intersting one in which Sozomen states that it was actually Arians who corrupted baptism by immersion by stating that it could properly be done with a single immersion rather than three immersions, as was the “tradition which has been carefully handed down to the present day.”
About this time, Eunomius (d. 393), who had held the church in Cyzicus in place of Eleusius, and who presided over the Arian heresy, devised another heresy besides this, which some have called by his name, but which is sometimes denominated the Anomian heresy. Some assert that Eunomius was the first who ventured to maintain that divine baptism ought to be performed by one immersion, and to corrupt, in this manner, the tradition which has been carefully handed down to the present day. He invented, it is said, a mode of discipline contrary to that of the Church, and disguised the innovation under gravity and greater severity….
But whether it was Eunomius, or any other person, who first made these innovations upon the tradition of baptism, it seems to me that such innovators, whoever they may have been, were alone in danger, according to their own representation, of quitting this life without having received the divine baptism; for if, after they had been baptized according to the mode recommended from the beginning, they found it impossible to rebaptize themselves, it must be admitted that they introduced a practice to which they had not themselves submitted, and thus undertook to administer to others what had never been administered to them by themselves nor by others. Thus, after having laid down the dogma by some non-existent principle and private assumption, they proceeded to bestow upon others what they had not themselves received. The absurdity of this assumption is manifest from their own confession; for they admit that the uninitiated have not the power to baptize others. Now, according to their opinion, he who has not been baptized in conformity with their tradition is unbaptized as one not properly initiated, and they confirm this opinion by their practice, inasmuch as they rebaptize all those who join their sect, although previously initiated according to the tradition of the Catholic Church.
Salminius Hermias Sozomenus, Ecclesiastical History, Book VI, Chapter 26