Pope Francis has defended the principle of freedom of speech, but said that it shouldn’t be abused to “provoke” or “insult” other people’s faith.

Speaking to journalists aboard the papal plane on his way to the Phillippines, the Pope unequivocally condemned the murder of journalists working for French satirical magazine Charlie Hebdo, but said that free speech was not an unlimited right, Crux reports.

“One cannot make war [or] kill in the name of one’s own religion, that is, in the name of God,” Francis said. “To kill in the name of God is an aberration.”

But, he added, speaking in Italian “One cannot provoke, one cannot insult other people’s faith, one cannot make fun of faith.”

He said people also shouldn’t be surprised when those attacked react to such taunts.

Even in the case of a dear friend, Francis said, “If he says a swear word against my mother, he’s going to get a punch in the nose. That’s normal.”

“People who make fun of, who toy with other people’s religions, he said, risk running into “what would happen to [that friend] if he said something against my mother.”

“Every religion has its dignity … and I cannot make fun of it,” the pope said. “In freedom of expression there are limits, like in regard to my mother.”

The Tablet reports that the Pope was also asked about the threat to his own life posed by Islamic extremists, who have talked about seeking to capture Rome.

“The best way to respond is always meekness,” he said, but pointed out he is “truly worried” about the safety of large number of Catholics who attend papal audiences at the Vatican.

“On this, I have spoken with Vatican security, who are charged with solving this,” he said.

He revealed his personal prayers to God about threats to his life.

“I have said to the Lord, don’t make me suffer pain. I am not courageous in front of pain. I am very, very timid.”