Roman Catholic scholars rebuked the former Pope Benedict on Monday for his comments in a new book regarding the delicate matter of priestly celibacy, saying his words were helping to destabilize the reigning Pope Francis.

It is not the first time that Benedict has spoken out on Church matters despite a public vow he made in 2013, when he became the first pontiff in 700 years to resign.

The situation also underscores the polarization between conservatives and progressives in the 1.3 billion-member Church.

“One pope is complicated enough. This is a mess,” John Gehring, Catholic Program Director at Faith in Public Life, a U.S. group, said in a tweet.

“With great respect to Benedict XVI, it’s time for him to live up to his promise to be ‘hidden from the world.”

In the book, “From the Depths of Our Hearts,” written with Cardinal Robert Sarah, 74, Benedict, 92 and in ill health, defends priestly celibacy in what appears to be a strategically timed appeal to Francis to not change the rules.

The book, Benedict’s first since his resignation, comes as Francis must decide whether to allow older married men with proven leadership qualities in the Amazon to be ordained priests in exceptional cases as a response to a shortage in the vast region.

The proposal was made during a contentious gathering of bishops at the Vatican in October and Francis will respond to it and other suggestions, including the role of women in the region, in a document expected to be published soon.

While Francis has not ruled out a limited change in a specific region, he has also strongly supported priestly celibacy in general.

Excerpts from the book were published on Sunday by the French newspaper Le Figaro. On Monday, the Vatican issued a statement reminding reporters that Francis supports celibacy as “a gift for the Church”.

Its timing, giving the perception that a retired pope may be trying to influence the decision of a reigning pope, was debated by Church commentators

Massimo Faggioli, a theologian at Villanova University in the United States, called it “a serious breach” by Benedict, adding that for many conservatives who oppose Francis “Benedict XVI never retired really”.

Kurt Martens, professor of canon law at the Catholic University of America in Washington, said: “A former pope should not speak in public about anything at all. He had his chance when he was in office. Now it belongs to his successor to govern”.

Benedict caused a stir last year by writing an essay for a German newspaper in which he blamed the Catholic Church’s sexual abuse scandal on the effects of the sexual revolution of the 1960s, homosexual cliques in seminaries and what he called a general collapse in morality.

Many Catholic theologians and abuse experts rebuked him, saying he was trying to shift the blame away from the Church.

Some commentators openly questioned whether others were using Benedict, saying he is too frail to have written a book and alleging that he can barely hold a conversation anymore.

His defenders strongly contested this.

“The (liberal Church) mafia is out to get Benedict XVI. He’s old, but he isn’t on his deathbed,” read a Tweet from the conservative Catholic blog Rorate Caeli.

“We pray for Benedict XVI: may the Lord keep the wolves from devouring him until the time comes of his natural departure from this earth,” Rorate Caeli said.

Matthew Schmitz, an editor at the conservative U.S. Catholic intellectual journal First Things, also backed the former pope.

“Benedict XVI and Cardinal Sarah have written an eloquent defense of celibacy, not an attack on Pope Francis,” he said in a tweet.

A personal assistant to Benedict was not immediately available for comment.