The early Church Fathers, of course, were unanimous in teaching the reality of mortal sin. They had to embrace the doctrine of mortal sin precisely because they recognized not only the salvific power of baptism but also the damning power of certain serious sins. The Church taught that “baptism . . . now saves you” (1 Pet. 3:21; see the Catholic Answers tracts Baptismal Grace and Born of Water and the Spirit). However, since during the persecutions some baptized people denied Christ, and since Christ taught that “whoever denies me before men, I also will deny before my Father who is in heaven” (Matt. 10:33), the Church Fathers recognized that it was possible to lose the grace of salvation after baptism.
In the Old Testament sin is set forth as an act of disobedience (Gen., ii, 16-17; iii, 11; Is., i, 2-4; Jer., ii, 32); as an insult to God (Num., xxvii, 14); as something detested and punished by God (Gen., iii, 14-19, Gen., iv, 9-16); as injurious to the sinner (Tob., xii, 10); to be expiated by penance (Ps. 1, 19). In the New Testament it is clearly taught in St. Paul that sin is a transgression of the law (Rom., ii, 23; v, 12-20); a servitude from which we are liberated by grace (Rom., vi, 16-18); a disobedience (Heb., ii, 2) punished by God (Heb., x, 26-31). St. John describes sin as an offense to God, a disorder of the will (John, xii, 43), an iniquity (I John, iii, 4-10). Christ in many of his utterances teaches the nature and extent of sin. He came to promulgate a new law more perfect than the old, which would extend to the ordering not only of external but also of internal acts to a degree unknown before, and, in His Sermon on the Mount, he condemns as sinful many acts which were judged honest and righteous by the doctors and teachers of the Old Law. He denounces in a special manner hypocrisy and scandal, infidelity and the sin against the Holy Ghost. In particular he teaches that sins come from the heart (Matt., xv, 19-20).
From Catholic Answers
The article said Jesus taught it! Where?
When Jesus spoke to Nicodemus He referred to being born of the water from the womb. Baptism before He sacrificed Himself on the cross was the outward sign of true repentence. Water baptism is not required to have God put His Holy Spirit Life in a person who is repentant and faithing in Jesus to Save them.
Indeed the Master taught that the heart issues are most important. He was a teacher of the Torah. A Rabbi. A Rebbe. He taught and expected all of his students to keep the entire Torah as He did. It was the mark of his movement that they fully walked and talked Torah in Love. Yeshua’s call to repentance was twofold: “Return to Torah and Renew your First Love as in the days of your youth.”
You have some documentation on that??? From what I've seen the early church fathers weren't unanimous on anything...