CAIRO — They came by the thousands, pouring through the ancient stone archways and into the gleaming white marble courtyard of al-Azhar mosque. The faithful had come to pray, to hear a thundering sermon from a leader of Hamas and to witness a rebirth.

Co-opted for decades by irreligious and autocratic Egyptian governments, al-Azhar was retaking its rightful place as the world’s leading voice of Sunni Islam, worshipers said. The presence of a once-banned Hamas preacher willing to speak incendiary truths was proof that the millennium-old mosque and university that bear the al-Azhar name had finally been set free.