Al-Baghdadi's purported appearance in Mosul, a city of some 2 million residents that the militants seized last month, came five days after his group declared the establishment of an Islamic state, or caliphate, in the territories it seized in Iraq and Syria. The group proclaimed al-Baghdadi the leader of its state and demanded that all Muslims pledge allegiance to him.
In the video, the man said to be al-Baghdadi says that "the mujahedeen have been rewarded victory by God after years of jihad, and they were able to achieve their aim and hurried to announce the caliphate and choose the imam," referring to the leader.
"It is a burden to accept this responsibility to be in charge of you," he adds. "I am not better than you or more virtuous than you. If you see me on the right path, help me. If you see me on the wrong path, advise me and halt me. And obey me as far as I obey God."
Speaking in classical Arabic with little emotion, he outlines a vision that emphasizes holy war, the implementation of a strict interpretation of Islamic law, and the philosophy that the establishment of an Islamic caliphate is a duty incumbent on all Muslims.
He is dressed in black robes and a black turban a sign that he claims descent from the Prophet Muhammad. He has dark eyes, thick eyebrows and a full black beard with streaks of gray on the sides.
At the beginning of the video, the man purported to be al-Baghdadi slowly climbs the mosque's pulpit one step at a time. Then the call to prayer is made as he cleans his teeth with a miswak, a special type of stick that devout Muslims use to clean their teeth and freshen their breath.
The camera pans away at one point to show several dozen men and boys standing for prayer in the mosque, and a black flag of the Islamic State group hangs along one wall. One man stands guard, with a gun holster under his arm.
Aymenn al-Tamimi, an expert on militant factions in Syria and Iraq, said al-Baghdadi has come under criticism since unilaterally declaring the establishment of a caliphate, in part for not appearing before the people.
"He had declared himself caliph; he couldn't hide away. He had to make an appearance at some time," al-Tamimi said. Traditionally, a Muslim ruler is expected to live among the people and to preach the sermon before communal Friday prayers.
The brazenness of his purported appearance nearly unheard of among the most prominent global jihad figures suggested the Islamic State's confidence in its rule of Mosul.
"The fact that he has done this without any consequences in Mosul's biggest mosque is a sign of [the Islamic State group's] power within the city," said al-Tamimi. He said it would likely boost the morale of al-Baghdadi's fighters and deal a blow to the group's rivals.
Another aspect of the rule al-Baghdadi envisions was made clear in a series of images that emerged online late Saturday showing the destruction of at least 10 ancient shrines and Shiite mosques in territory his group controls.
The 21 photographs posted on a website that frequently carries official statements from the Islamic State extremist group document the destruction in Mosul and the town of Tal Afar. Some of the photos show bulldozers plowing through walls, while others show explosives demolishing the buildings in a cloud of smoke and rubble.
Residents from both Mosul and Tal Afar confirmed the destruction of the sites.
Sunni extremists consider Shiites Muslims heretics, and the veneration of saints apostasy.
Also Saturday, Iraqi Prime Minister Nouri al-Maliki removed the chief of the army's ground forces and the head of the federal police from their posts as part of his promised shake-up in the security forces after their near collapse in the face of the militant surge.