Pope Francis on Thursday said there are limits to freedom of expression when it comes to religion, referencing the Charlie Hebdo massacre in Paris.

His remarks came on board the papal plane as it was flying to Manila as part of his ongoing tour of Asia.

"Every religion has its dignity," the pope said, according to NBC News. "One cannot provoke, one cannot insult other people's faith, one cannot make fun of faith," he added.

Killing in the name of religion, he said, is an "absurdity," AFP reported.

The pope said he defended freedom of expression, but that insulting religion goes too far.

The Associated Press reported:

By way of example, he referred to Alberto Gasparri, who organizes papal trips and was standing by his side. He said: "If my good friend Dr. Gasparri says a curse word against my mother, he can expect a punch. It's normal. It's normal. You cannot provoke. You cannot insult the faith of others. You cannot make fun of the faith of others."



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"There are so many people who speak badly about religions or other religions, who make fun of them, who make a game out of the religions of others," he said. "They are provocateurs. And what happens to them is what would happen to Dr. Gasparri if he says a curse word against my mother. There is a limit."

The pope also said that global warming was "mostly" the fault of humans, the AP reported:

"I don't know if it (human activity) is the only cause, but mostly, in great part, it is man who has slapped nature in the face," he said. "We have in a sense taken over nature."