He said that all Muslims are affected by Israel allowing Jews to visit the Temple Mount, and this will lead to the war, "and the Muslims will win," he stated.
Al-Mahdi stressed that Muslims must be patient, and ensure that they strengthen sufficiently before the ultimate battle, quoting Islamic sources on the virtues of patience.
The sheikh added that the Al-Aqsa Mosque belongs to all Muslims and the responsibility lies on every Muslim to free it from "the Zionist abomination."
Al Azhar is considered a relatively moderate Islamic institution in Egypt.
UPDATE: It appears that this may have been part of an official anti-Israel rally organized by the Muslim Brotherhood:
Egypt’s Muslim Brotherhood is staging an anti-Israel rally in Cairo to protest Israeli airstrikes in Syria and the detention of a Muslim cleric.(h/t Ian)
Chants of “the people want destruction of Israel” rang out Friday inside Al-Azhar mosque, the centuries-old seat of Sunni Muslim learning.
The rally is the first such protest by the Brotherhood, from which Egyptian President Mohammed Morsi hails, since it gained prominence after 2011 uprising that ousted president Hosni Mubarak.
Group officials say they are protesting the Israeli detention of top Palestinian Muslim cleric in the Holy Land in a rare crackdown on a leading religious figure that drew fierce condemnation from Palestinians. The demonstrators also were denouncing Israeli airstrikes in Syria that targeted alleged shipments of advanced Iranian missiles thought to be bound for Hezbollah.
UPDATE 2: A different preacher in Egypt today said that it would be preferable to demolish the Al Aqsa Mosque than to let Jews pray there.