Millions of Muslims making the annual pilgrimage to their holiest site, Mecca, flock to get a share of spring water they believe originates in heaven and is endowed with healing power.
The spring, named Zamzam, has according to Muslim belief run uninterrupted for some 4,000 years, from the time of prophet Abraham and his son Ishmael.
The 31-metre (105-foot) deep source is located inside the Grand Mosque complex and its water is used to wash the holy Kaaba stone at the Grand Mosque ahead of the annual pilgrimage or hajj, which this year formally begins on Monday.
Worshippers in the Grand Mosque are able to drink Zamzam from hundreds of scattered taps.
Because of belief in its healing power, there is a rush during every hajj -- when some two million Muslims converge on Mecca -- to collect some of the precious water for family members and friends who could not make the journey to Mecca.
"I am taking some for my relatives back home, some of them are very sick people suffering from chronic diseases," said Jamal, an Arab pilgrim.
"I've seen it work miracles for a sick friend before," he added while buying a jerry can from a Saudi vendor.
"It only heals if you are a true believer, you should believe that Allah will not leave his people alone," said Fatemeh, an elderly woman pilgrim from Iran.
Every hajj, there is run on plastic, 20-litre (quart) jerry cans to carry the sterilized Zamzam waters back to the four corners of the globe.
Some entrepreneurs have identified a niche market, filling up jerry cans and selling them as "Zamzam water" closer to the hotels of pilgrims, supposedly to save them the trouble of carrying heavy containers back from the source.
Hamad, a Saudi national, warned: "If you are buying the filled cans on the road out of the city, well it is between you and Allah whether it is genuine or not."
"At 15 riyals (four dollars, three euros) a can for Zamzam water, I sell a few per day, praise be to Allah," said a teenage boy who declined to give his name.
"Such selling is not allowed and the municipality is fighting this matter," said Mohsen al-Solami, director of The Two Holy Mosques Exhibition, an educational display to inform pilgrims about renovations or changes at both Mecca's Grand Mosque and the Prophet Mohammad's mosque in Medina, farther north.
Among the exhibits is one on a metal case at the mouth of the Zamzam well, though little is known about the exact source of the water that feeds the spring.
Muslims believe Zamzam came into being to provide Hagar, Abraham's wife, and her baby Ishmael with water in the hot dry valley of Mecca where God ordered Abraham to leave them.
In her desperate search for water for the baby, Hagar ran seven times between the hillocks of Safa and Marwa until she saw water running between the legs of her baby.
Part of the hajj is called "Saiy", a run between Safa and Marwa in commemoration of Hagar's run in search of water.
"The water from this spring is miraculous. It has been flowing for more than 4,000 years. No additional water has been added to it," Solami told AFP, shrugging off questions on whether water is added to meet the demands of pilgrims.
"There are two sources for the spring, one from the Grand Mosque which is the bigger source and the other from Safa."
"The water is even taken by tankers to the Prophet Mohammad's mosque in Medina," he said.