Card. Jean-Louis Tauran receives Sheik Ahmed el-Tayyib, Grand Imam of Al-Azhar Mosque, as he arrives for his audience with Pope Francis in the Apostolic Palace, at Vatican, Monday, May 23, 2016 (AP)

Card. Jean-Louis Tauran receives Sheik Ahmed el-Tayyib, Grand Imam of Al-Azhar Mosque, as he arrives for his audience with Pope Francis in the Apostolic Palace, at Vatican, Monday, May 23, 2016 (AP)

Sheik Ahmed el-Tayyib, Grand Imam of Al-Azhar Mosque, arrives with archbishop Georg Ganswein, right, and cardinal Jean-Louis Tauran, left, to meet Pope Francis during a private audience in the Apostolic Palace, at the Vatican, Monday, May 23, 2016 (AP)

Sheik Ahmed el-Tayyib, left, Grand Imam of Al-Azhar Mosque, exchange gifts with Pope Francis during a private audience in the Apostolic Palace, at the Vatican, Monday, May 23, 2016 (AP)

Sheik Ahmed el-Tayyib, left, Grand Imam of Al-Azhar Mosque, exchange gifts with Pope Francis during a private audience in the Apostolic Palace, at the Vatican, Monday, May 23, 2016 (AP)

Sheik Ahmed el-Tayyib, left, Grand Imam of Al-Azhar Mosque, talks with Pope Francis during a private audience in the Apostolic Palace, at the Vatican, Monday, May 23, 2016 (AP)

Sheik Ahmed el-Tayyib, Grand Imam of Al-Azhar Mosque, talks with Pope Francis during a private audience in the Apostolic Palace, at the Vatican, Monday, May 23, 2016 (AP)

Sheik Ahmed el-Tayyib, Grand Imam of Al-Azhar Mosque, talks with Pope Francis during a private audience in the Apostolic Palace, at the Vatican, Monday, May 23, 2016 (AP)

Sheik Ahmed el-Tayyib, Grand Imam of Al-Azhar Mosque, talks with Pope Francis during a private audience in the Apostolic Palace, at the Vatican, Monday, May 23, 2016 (AP)