Bishop Mar Mari Emmanuel was addressing the congregation at Christ The Good Shepherd Church in Wakeley, western Sydney, on April 15 when he was allegedly attacked.

He was taken to hospital with lacerations to his head and another of the parish priests, Father Isaac Royel, was also injured.

In an audio message shared by the church on April 18 the bishop reassured followers he was fine and recovering quickly.

"I forgive whoever has done this act and I say to him 'you are my son, I love you and I will always pray for you'," Bishop Emmanuel said.

"To our beloved faithfuls, we need to reflect Christ in our life.

"The Lord Jesus never said go out and fight in the street, never said to retaliate but to pray and this is what I'm asking everyone to do."

NSW premier Chris Minns said the bishop's words were "exactly the message" Sydney needed to hear.

"That gesture was really important and it was echoed by every major faith and religious leader in the state over the last 48 hours," Mr Minns said.

A 16-year-old boy was arrested at the church and remains in hospital after surgery for injuries to his hand.

The NSW Joint Counter Terrorism Team is investigating the alleged stabbing which NSW Police Commissioner Karen Webb declared a religiously motivated "terrorist act".

Meanwhile a 19-year-old from Doonside has been charged after hundreds of people rioted outside church in the aftermath of the alleged stabbing.

The teenager has been charged with riot, affray and destroy/damage property during a public disorder and was refused bail to appear in court on April 18.

Commissioner Webb said the teenager was not a member of the parish.

Two police officers were seriously injured, one with a broken jaw, and 20 police cars damaged in violent scenes outside Christ The Good Shepherd Church.

Paramedics were forced to shelter inside the church after the crowd "turned on police", NSW Police Commissioner Karen Webb said.

Those involved were told to "expect a knock at the door".

"Police officers were doing their job and they were attacked," Commissioner Webb said on April 16.

"People used what was available to them in the area including bricks, concrete, palings, to assault police and throw missiles at police."

Commissioner Webb said up to 50 people could be arrested in connection to the riot and called for anyone with information to contact police.

Political leaders called for calm after the riot with Premier Chris Minns meeting with faith leaders to unanimously condemn the violence.

"There is no such thing in Australia as taking the law into your own hands," Mr Minns said.

Anyone with information about extremist activity or possible threats to the community is urged to contact the National Security Hotline on 1800 123 400.