The Iranian, Mohammad Kheirkhah, later joined other pilgrims in a feast of freshly slaughtered sheep, goats and camels at a huge tent city in Mina, a desert valley east of Islam's holiest city, Mecca.
Similar sacrifices, marking the start of the Eid al-Adha, or Feast of the Sacrifice, were carried out by Muslims around the world.
The holiday commemorates a story celebrated by Muslims, Jews and Christians in which God asked the prophet Abraham to sacrifice his son to prove his faith, but then in the end offered a sheep to kill instead.
Muslim tradition says it was at Mina, 5 kilometres from Mecca, that the devil tried to tempt Abraham to disobey God by refusing to sacrifice his son. Hordes of pilgrims dressed in their white robes streamed across Mina valley on Monday toward three walls symbolizing the devil known as the Jamarat, chanting "at thy service, my God, at thy service."
The massive crowds streamed through a four-storey platform the size of an airport terminal built around the walls, and each pilgrim stoned the largest wall with pebbles collected earlier on the nearby rocky plain of Muzdalifah.
They will return on each of the final two days of the five-day pilgrimage, which ends on Wednesday, to stone all three walls.
The stoning ritual has caused frequent stampedes that have killed more than a thousand pilgrims in past pilgrimages.
More than 1,400 people were killed in 1990 in a stampede in a tunnel leading to the Jamarat. In 2006, over 360 people died in a similar incident while they were on a platform performing the stoning ritual.
Colonel Khaled al-Mahmadi, the head of security at the Jamarat, said precautionary measures have been taken to avoid a stampede - including expanding the Jamarat platform from two to the current four stories to provide more room for the pilgrims.
"We have become experts in crowd management after handling enormous gatherings on the Jamarat over the years," he said.
Al-Mahmadi said authorities have banned pilgrims from carrying baggage during the stoning because it can cause people to stumble and fall, causing panic and injuries.
Police have also set up one-way routes to and from the Jamarat monitored by cameras to avoid congestion.
Helicopters flew overhead on Monday to monitor the crowd, and policemen and volunteers on the streets called out, "Yalla, ya hajj" - "Hurry up, pilgrim."
After the stoning, many of the male pilgrims shaved their heads - the mark of a Muslim who has completed the hajj. Female pilgrims cut a clip of their hair.
"Now, I feel the burden of sin is off my shoulders. I feel free and purified," said Kheirkhah, the Iranian pilgrim.
Bunches of hair littered the pavement around him at the foot of the Jamarat platform.
Islam requires that all Muslims who are financially and physically able to perform the hajj at least once in their lifetime. The pilgrimage is supposed to cleanse Muslims of their sin.
The hajj begins and ends in the holy city of Mecca, the birthplace of the 7th century Prophet Mohammed and the site of Islam's holiest shrine, the Kaaba.
