Hours before sunrise Thursday, thousands of Muslims from around the world stood in the dark on a rocky desert hill, preparing for prayers on the first day of the annual hajj pilgrimage, a central pillar of their faith.

Muslims believe that prayer on Mount Arafat is their best chance to erase past sins and start anew.

The four-day hajj features millions packed shoulder to shoulder in prayer and supplication. According to Islam, each able-bodied believer must make the pilgrimage once.

"Let all your feuds be abolished," the Prophet Muhammad said in his last sermon on the hill called Jabal al-Rahman, Mountain of Mercy, in the area of Mount Arafat. "You must know that every Muslim is the brother of every Muslim...between Muslims there are no races and no tribes...do not oppress and do not be oppressed."

Some 1,400 years later, Muslims believe on this day and at this place, the gates of heaven are open for prayers to be answered and sins to be forgiven.

"I have feelings that cannot be described in words. We thank God for the chance to perform the hajj here and visit God's house in Mecca," said Mustafa Daama, 27, from Mauritania.

On other parts of the mountain, Muslims chanted in unison, "Labayk Allahuma Labayk," or "Here I am, God, answering your call. Here I am."

Muslims believe the hajj traces the paths of the Prophets Abraham, Ishmael and Muhammad. The hajj typically concludes as it began, with a set of rituals at the Kaaba, the cube-shaped structure in Mecca's Grand Mosque that observant Muslims around the world face in prayer five times a day.

Technology and the modern world have changed the atmosphere surrounding the hajj.

For centuries, the rocky mountain was a quiet place for contemplation and serene prayers. Now it is crowded with pilgrims pushing and shoving to take pictures with their iPads and mobile phones.

Adding to the tumult, ultraconservative men with loudspeakers yelled at pilgrims to stop crowding the hill, saying the whole area of Mount Arafat is sacred and that men and women should avoid the inevitable brushes of physical contact.

Ignoring their calls, many pilgrims were uploading their pictures online from the hilltop to share instantly with friends and family, while others used touch screens to read the Quran, rather than carrying it in printed form.

Casually dressed photographer Bandar Maarouf, 22, from Yemen, stood out from the sea of pilgrim men who wear white seamless garments and seamless sandals meant to represent equality and unity.

Wearing a bright pink shirt, low slung jeans and a hat turned sideways, he was taking photos for pilgrims at around $3 apiece. His camera prints the photos on the spot. He expected to sell at least 400 photos on Thursday.

"This season helps a person live. (I earn) some from here and there, and God is always giving," he said.

Some of the pilgrims' prayers had to do with current events.

Carrying a large Sudanese flag, Mohamed Ali said he was praying for an end to the civil war in Syria and victory for rebels over President Bashar Assad. "Victory is close, God willing," Ali said.

"May God bring Muslims together and help us unify, and help our Christian brothers, even those who made the film against the Prophet Muhammad," he said, referring to a movie that sparked violent protests last month around the Islamic world.

Others had more personal prayers.

An Egyptian mother of three, Nadia Abdel Aziz, appealed emotionally to God to make her children behave more kindly toward her. The 65-year-old widow said she was able to perform the hajj with the help of donations from a mosque in Cairo.

"O God! I want my kids to come and see me and be sensitive toward me, as I see with other families," she cried.

With her arms outstretched, she begged God for salvation, wiping a stream of tears from her face.

Saudi officials say about 3.4 million Muslims from all corners of the world are making the pilgrimage this year.

A sea of millions dressed in white, some waving their national flags, stretched for miles in the area of Mount Arafat, many chanting in unison, their prayers echoing.

Mount Arafat, about 20 kilometers (12 miles) east of Mecca, is a required stop for Muslims during the hajj.

As the sun and temperatures rose Thursday, tens of thousands of pilgrims began climbing the Mountain of Mercy.

At sunset, pilgrims headed to Muzdalifa, where Muslims believe prophets before Muhammad once prayed. There, they collected pebbles walking or driving to nearby Mina for Friday's symbolic stoning of the devil that marks the start of Eid al-Adha, or feast of the sacrifice, when Muslims slaughter lambs to feed the hungry.

They made the 8 kilometer journey from Mount Arafat by foot and bus caravan, where they will spend the night, as the Prophet Muhammad did during his own pilgrimage. Millions of people will sleep there in tents.

Hajj rules — based on centuries of interpretation of the Sunna, the traditions of Muhammad — are extremely elaborate. Pilgrims must all gather at certain sites at specific times. Some rites are repeated, others are partially repeated and some performed only once.

Many pilgrims being their journey in the Saudi Arabian city of Medina with a visit to Muhammad's mosque, where he is buried. They then head to Mecca and perform a set of pre-hajj rituals, including circling the Kaaba counterclockwise with their hearts tilted toward it — the same rituals that conclude the hajj for many.