Millions of pilgrims are arriving in Mecca for Islam's annual Hajj pilgrimage that began on Wednesday, a journey all Muslims must perform at least once in their lifetime, if they are able to make the expensive, difficult journey.

To give you a sense of what it entails, here is a feed of the Makkah Live Stream channel on YouTube.

The pilgrimage is a duty for both Sunnis and Shias, yet it comes at a time when tensions in the Muslim world are running high over the conflict in Syria that has killed more than 30,000, and has divided Muslims all over the globe.

Despite a call from Saudi Arabia's top cleric for unity and a pilgrimage free from nationalist sentiment, Syrian pilgrims have raised rebel flags as they participate in the holy ritual.

I was joined by Dena Takruri, HuffPost Live Producer, and Reverend Paul Raushenbush, HuffPost Senior Religion Editor; Zuleqa Husain, Al Jazeera English Producer; Ebrahim Moosa, Professor of Islamic Studies at Duke University; Najeeba Syeed Miller, Assistant Professor at the Claremont School of Theology; and Qasim Rashid, Author of the upcoming book "The Wrong Kind of Muslim."

Click through to see photos from this year's Hajj pilgrimage:

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  • Muslim pilgrims circle the Kaaba as they pray inside and outside the Grand mosque in Mecca, Saudi Arabia, Monday, Oct. 22, 2012. The annual Islamic pilgrimage draws three million visitors each year, making it the largest yearly gathering of people in the world. (AP Photo/Hassan Ammar)

  • Muslim pilgrims pray outside the Grand mosque in Mecca, Saudi Arabia, Monday, Oct. 22, 2012. The annual Islamic pilgrimage draws three million visitors each year, making it the largest yearly gathering of people in the world. (AP Photo/Hassan Ammar)

  • Muslim pilgrims circle the Kaaba as pray inside and outside the Grand mosque in Mecca, Saudi Arabia, Monday, Oct. 22, 2012. The annual Islamic pilgrimage draws three million visitors each year, making it the largest yearly gathering of people in the world. (AP Photo/Hassan Ammar)

  • Muslim pilgrims pray inside the Grand mosque in Mecca, Saudi Arabia, Monday, Oct. 22, 2012. The annual Islamic pilgrimage draws three million visitors each year, making it the largest yearly gathering of people in the world. (AP Photo/Hassan Ammar)

  • Muslim pilgrims circle the Kaaba as pray inside and outside the Grand mosque in Mecca, Saudi Arabia, Monday, Oct. 22, 2012. The annual Islamic pilgrimage draws three million visitors each year, making it the largest yearly gathering of people in the world. (AP Photo/Hassan Ammar)

  • Muslim pilgrims circle the Kaaba as pray inside and outside the Grand mosque in Mecca, Saudi Arabia, Monday, Oct. 22, 2012. The annual Islamic pilgrimage draws three million visitors each year, making it the largest yearly gathering of people in the world. (AP Photo/Hassan Ammar)

  • Muslim pilgrims circle the Kaaba as pray inside and outside the Grand mosque in Mecca, Saudi Arabia, Monday, Oct. 22, 2012. The annual Islamic pilgrimage draws three million visitors each year, making it the largest yearly gathering of people in the world. (AP Photo/Hassan Ammar)

  • Muslim pilgrims circle the Kaaba as pray inside the Grand mosque in the holy city of Mecca, Saudi Arabia, Tuesday, Oct. 23, 2012. The annual Islamic pilgrimage draws three million visitors each year, making it the largest yearly gathering of people in the world. (AP Photo/Hassan Ammar)

  • Muslim pilgrims circle the Kaaba as pray inside the Grand mosque in the holy city of Mecca, Saudi Arabia, Tuesday, Oct. 23, 2012. The annual Islamic pilgrimage draws three million visitors each year, making it the largest yearly gathering of people in the world. (AP Photo/Hassan Ammar)

  • Muslim pilgrims shop at a market near the Grand Mosque in the holy city of Mecca, Saudi Arabia, Tuesday, Oct. 23, 2012. The annual Islamic pilgrimage draws three million visitors each year, making it the largest yearly gathering of people in the world. (AP Photo/Hassan Ammar)

  • A Muslim pilgrim buys rosaries at a market near the Grand Mosque in the holy city of Mecca, Saudi Arabia, Tuesday, Oct. 23, 2012. The annual Islamic pilgrimage draws three million visitors each year, making it the largest yearly gathering of people in the world. (AP Photo/Hassan Ammar)

  • Muslim pilgrims head to Mount Arafat ahead of the hajj main ritual in the holy city of Mecca, Saudi Arabia, Wednesday, Oct. 24, 2012. Saudi authorities say around 3.4 million pilgrims some 1.7 million of them from abroad have arrived in the holy cities of Mecca and Medina for this year's pilgrimage. (AP Photo/Hassan Ammar)

  • Muslim pilgrims head to Mount Arafat ahead of the hajj main ritual in the holy city of Mecca, Saudi Arabia, Wednesday, Oct. 24, 2012. Saudi authorities say around 3.4 million pilgrims some 1.7 million of them from abroad have arrived in the holy cities of Mecca and Medina for this year's pilgrimage. (AP Photo/Hassan Ammar)

  • Muslim pilgrims head to Mount Arafat ahead of the hajj main ritual in the holy city of Mecca, Saudi Arabia, Wednesday, Oct. 24, 2012. Saudi authorities say around 3.4 million pilgrims some 1.7 million of them from abroad have arrived in the holy cities of Mecca and Medina for this year's pilgrimage. (AP Photo/Hassan Ammar)