The majority of pilgrims arrived after sunrise in Arafat, a small plain about 250 metres above sea level surrounded by mountains in western Saudi Arabia.
"Here I am God, at Your command," chanted the pilgrims as they marched under the blazing sun.
"Go, go, go," shouted policemen over loudspeakers as the sounds of sirens and the din of the massed worshippers filled the air.
In the rush to leave, Saudi police and security forces struggled to prevent the masses on foot from obstructing the buses and trucks transporting other pilgrims.
Tracing a journey made by Prophet Mohammed more than 1,400 years ago and following a tradition they believe was laid down by Abraham before him, pilgrims gathered for an emotional assembly in Arafat.
They prayed for mercy and forgiveness at the scene of the Prophet's last sermon.
Some also believe it was the place where Adam and Eve reunited after being banished from paradise.
Wukuf
The rite of Wukuf, or standing, before sunset on Arafat is the high point of the Hajj.
Without it the journey would be considered incomplete.
Pilgrims, holding umbrellas over their heads or wheeling their weak relatives, pressed ahead shoulder-to-shoulder towards the 70-metre-high Jabal al-Rahma, or the Mount of Mercy, where many believe their prayers will be better heard.
Towers sprinkled mist on the faithful as they listened under the scorching sun to the Saudi mufti, the highest religious authority in the ultra-conservative kingdom.
From Namera Mosque – and broadcast to many of the pilgrims from huge loudspeakers - Sheikh Abdul Aziz al-Sheikh urged Muslims to unite, return to the essence of Islam and shun terrorism.
"What's known as terror is forbidden under Islamic doctrine," said the blind cleric.
"Islam is being unjustly targeted through an effort to attribute the philosophy of terror to this religion,"
"Some have committed a great offence against Islam, as the things that they have done have led to the concept of terrorism being linked to this religion," he added.
The Sheikh also called on pilgrims to shun Western ideas, which he said were aimed at destroying their religion under the guise of women's and human rights.
Previous years have seen Sheikh Abdul Aziz use the Hajj sermon as an opportunity to criticise Western media and governments for propagating a "distorted" image of Islam.
Stoning the Devil
After the Arafat prayers, crowds gather in Muzdalifa, where they are expected to spend the night in tents.
In Muzdalifa, the pilgrims collect pebbles for the symbolic stoning of the devil in Mina, after which they head to Mecca at the start of the Eid al-Adha (Feast of Sacrifice) holiday, the most important on the Islamic calendar.
The riskiest rite of the Hajj, it involves throwing pebbles into a pit at three pillars symbolising the powers of Satan.
The area was the scene of several tragedies including a stampede in 2003 that killed 251 pilgrims and another one in 1990 that killed 1,426.
Kaaba cloth change
The cloth of the Kaaba, the large cubic stone structure in Mecca towards which Muslims orient themselves when in prayer, has been replaced with a new one.
The careful task supervised by the President of the Grand Mosque and Prophetic Mosque Affairs Sheikh Saleh al-Haseen and Kaaba's Head Custodian Sheikh Abdul-Aziz al-Shaibi.
Every year, the Kaaba's cloth is replaced with a new one the day
before Eid Al-Adha.
Costing nearly $6 million (AUD) the 14-metre high and 47-metre long five-piece cloth was made of 450 kg of natural black-dyed silk that contains verses from the Muslim holy book, the Koran, embroidered with golden threads.
In 1998, the Saudi government established a factory to handle manufacturing the cloth and souvenirs given to senior officials.
The Kaaba itself gets washed twice a year.
Twelve emergencies
As pilgrims perform their religious duties, Saudi authorities have set up five civil defence centres, 26 rescue teams, 1,124 fire rescue networks, as well as deploying many security and safety personnel.
In the aftermath of the death of 76 people on Thursday, in the collapse of an aging hostel, the head of civil defense operations for the western region, General Adel Zamzami, said his forces were prepared for 12 major potential emergencies.
These include fires, stampedes, torrential rain, food poisoning, terror acts and even chemical attacks.