The only kind of fanaticism that is acceptable to God is being fanatical about loving and helping others, Pope Francis said on his final day in Egypt.

"I hope that this visit will be an embrace of consolation and of encouragement to all Christians in the Middle East," the pope said.

Pope Francis "will affirm that there is a certain solidarity among Christians" and that "we are all related together by Jesus."

Pope Benedict said his heart was filled with gratitude "for the 90 years the good Lord has given me. There have been trying and difficult times, but he always guided me and pulled me through."

Despite recent and repeated terrorist attacks against Egypt's minority Christian communities, Pope Francis will not cancel his visit to Egypt.

The 460-page commemorative volume gathers just a slice of the kind of rigorous research still being done today "in the light of faith," and in the footsteps of a 90-year-old pope.

"The devil always comes in through the pocket, always," the pope said.

The pope told the participants that his first reaction to hearing about "this praiseworthy initiative" was one of gratitude to God.

A number of nations—many of which already possess nuclear arms—were boycotting the negotiations to ban such weapons.

The invitation came amid increasingly closer relations between the Vatican and al-Azhar University, which is considered the most authoritative theological-academic institution of Sunni Islam.