A senior rabbi feared his friend would be charged and jailed if a rabbinical organisation encouraged sexual abuse victims to come forward.
Rabbi Yosef Feldman wrote to a senior judge of Jewish court, Sydney Beth Din, in 2011 to object to a statement it was going to release about child sex abuse, fearing it would have implications for his friend, David Cyprys.
Cyprys was convicted and jailed for eight years in 2013 for abusing nine boys at Yeshivah Melbourne.
Rabbi Feldman told a royal commission on Friday he didn't know when he wrote to the Beth Din whether allegations against Cyprys were true or not.
The commission is holding public hearings in Melbourne into the response of Jewish community leaders at Yeshivah Melbourne and Yeshiva Bondi to reports of child sex abuse.
Counsel assisting Maria Gerace read from Rabbi Feldman's 2011 email, which was sent to Rabbi Moshe Gutnick.
"I have a problem with this statement because its going to have some factual ramifications for a friend of mine, who I have heard, who has repented for (child sex abuse) acts," Ms Gerace read.
"I believe his life and family are being ruined now for no good reason."
Rabbi Feldman told the commission he was upset Cyprys was being vilified without being found guilty.
"He was already vilified as though he was a sex abuser. I felt that he was being totally mistreated."
The commission was also told that during an email series in 2011 Rabbi Feldman argued rabbis should investigate the truth of a complaint before approaching authorities.
He later admitted he has since concluded all allegations should be handled by police, regardless of the outcome.
Rabbi Feldman also revealed his role in the investigation of the 2002 allegations made against a rabbinical student, known as AVL, at the Yeshiva Gedolah in Sydney where Rabbi Feldman was administrative director.
AVL fled to the United States just 48 hours after the sex abuse complaint and just hours after a meeting with Rabbi Feldman and his father Rabbi Pinchus Feldman.
Rabbi Feldman said AVL had admitted lying down and massaging the victim but said he did not believe, then, that it would fall into the category of child sex abuse.
Ms Gerace then questioned whether Rabbi Feldman knew in 2002 it was against the law for an adult to touch the genitals of a child.
He responded: "I didn't know that as a fact".
Rabbi Feldman also revealed that in 2002 he was probably unaware of his mandatory reporting responsibilities under NSW law.
He will continue to give evidence when the hearings resume on Monday.
