As a matter of historical fact, there was a general consensus among the Fathers that baptism was the instrument of regeneration and washing away of sin. That settles the question for the Roman Catholic, who is also amazed that Evangelical Christians have the audacity to disagree with the Fathers on this matter. It may come as a surprise that Catholics too do not follow the practice of the early church in the administration of this sacrament. For example it was common practice that the candidate was immersed three times, whereas the modern Catholic rite consists of pouring water on the head. Before baptism, the candidate was anointed with "oil of exorcism" while the presbyter prayed, "Let all spirits flee far away from you." Apart from the fact that there is no scriptural warrant for this anointing, they were also mistaken in their belief that this oil served for the remission of sins even before baptism:

Now this is blessed by the high priest for the remission of sins, and the first preparation for baptism. For he calls thus upon the unbegotten God, the Father of Christ, the King of all sensible and intelligible natures, that He would sanctify the oil in the name of the Lord Jesus, and impart to it spiritual grace and efficacious strength, the remission of sins, and the first preparation for the confession of baptism, that so the candidate for baptism, when he is anointed may be freed from all ungodliness, and may become worthy of initiation, according to the command of the Only-begotten (Apostolic Constitutions, XLII)

During baptism, the candidates had to remove their clothing and stand naked in the water. The newly baptized was not allowed to take a bath for a whole week. We do not feel obliged to follow the fathers in their unscriptural inventions, changing the simple ordinance of Christ into a superstition, not to mention their disregard for public decency. (See Tertullian, The Crown; St Hippolytus of Rome, The Apostolic Tradition). These are the same people who insisted on baptismal regeneration. 

However, to their credit, we should note that there was an emphasis in the early church on faith and repentance, so that the candidates of baptism were thoroughly indoctrinated in Christian doctrine before they were actually baptized. What should we think of a person who, having learned about Jesus, the cross and the resurrection, repents of his sins and believes in Christ for salvation? Do you think that he would not be saved until he was baptized in water? I don’t think so because the Bible everywhere teaches that those who believe in Jesus’ name are saved (Luke 7:50; John 20:31; Acts 10:43; 16:31; Romans 3:22, 25, 26, 28, 30, 4:5; Galatians 2:16; 3:24; Ephesians 2:8-9; Philippians 3:9, etc.).

The idea of baptismal regeneration is linked to infant baptism. Though the Bible teaches that baptism should follow personal faith in Christ, and though there is no conclusive scriptural evidence for baptizing infants, yet this tradition gradually increased in popularity until it became the common practice in the churches. The teaching about baptism effecting salvation was erroneous but not fatal because it was still linked to repentance and faith in Christ. But in infant baptism, baptism was separated from personal faith. The baby, though unable to believe, was supposedly cleansed from sin without even knowing about it! One error leads to another. Who knows how many people mistakenly think they are Christians simply because they were baptized in infancy? But here too, I hope that later on many came to a personal faith in Christ and were saved despite that false doctrine of baptismal regeneration.

In brief, we must have the courage to return to the revealed truth of the Bible even though our spiritual ancestors believed differently. They were mistaken in this area. We are not disrespectful to the Church Fathers, but our commitment to the ultimate authority of the Bible compels us to be different. The consistent Biblical pattern is firstly, the preaching of the Gospel, followed by faith, and finally the baptism of believers. Their faith in Christ is the irrefutable evidence that they are already born again before they enter the water of baptism. "These things have I written unto you that believe on the name of the Son of God; that ye may know that ye have eternal life" (1 John 5:13).