Millions of Muslims denied themselves food, cigarettes and water before setting off on an all-night ritual of feasting, family gatherings and entertainment on Friday, the first day of fasting in the holy month of Ramadan.

The disparity between nighttime and daytime during Ramadan astounds foreigners, delights merchants and disgusts clerics who urge piety 24 hours a day.

The Ramadan rituals stem from the belief that the first verses of the Koran, Islam's holy book, were revealed to the prophet Muhammad during these four weeks in the 7th century.

To honor the revelation, Muslims abstain from eating, drinking, smoking and sex between dawn and dusk. Muslims have observed the holy month for centuries, and it has come to be interpreted in many ways.

"Ramadan is a month of generosity," said Imam Abdel Aal, who fumigates streets against mosquitoes for the Cairo city government.

He and his wife squatted in a city park just after sunset, finishing a meal of beef, rice and vegetables donated by a nearby mosque. During Ramadan, most mosques donate thousands of meals every night to low-income people at "tables of mercy."

"Excellent. It had meat," Abdel Aal said, beaming.

Clerics urge their communities to use the month to cleanse their souls, denying themselves pleasures to encourage holy thoughts.

"When a person starves, he will have more power to restrain himself from sin, such as sex outside marriage," said Aid Abdel Hamid Youssef, a senior cleric at Al-Azhar in Cairo, the foremost theological institute in the Sunni Muslim world.

Fasting may not necessarily lead to spirituality, but life does wind down during Ramadan. Banks and government offices close early. Guards sit on curbs, their faces drawn with hunger pangs, thirst and fatigue. Workers rush home to prepare the evening feast -- iftar -- that begins at dusk. They rise before dawn, or never sleep at all, for the morning meal of suhur.

"One is saddened to see today (that) many people view the month of Ramadan as a time for sleep, laziness and, therefore, of decreased productivity," columnist Khaled Maeena wrote Friday in the Saudi newspaper Arab News.

The flipside is that Ramadan nights have become a time for excess. Lebanese television channels have spent a week broadcasting programs on what to cook for iftar. Nutritionists took to the airways to warn of the perils: Don't binge on your favorite dishes, avoid animal fats and use as little oil as possible.

In Jordan, housewife Issra' al-Araj, a mother of five, said the meaning of Ramadan has been turned on its head. Nowadays, she said, Muslims "fast to eat more and spend more."

In Riyadh, a columnist for Al-Watan agreed. Mohammed Rotayyan said Arab news media now provide TV serials and other entertainment that have nothing to do with Ramadan.

"If you asked any child on any Arab street about Ramadan, he won't say: 'It's the month of mercy and forgiveness.' He will say: 'It's the month of serials and contests,' " Rotayyan wrote.

There is also a political side to Ramadan. The insurgency in Iraq has intensified in the past three days, much as it did at the start of Ramadan last year. Muslim extremists are said to believe they will receive a fast ticket to paradise if they die "fighting for Islam" during the holy month.

In Cairo, sellers of dates -- the traditional fast-breaking fare -- sometimes give their fruit provocative names.

At the el-Sahel market opposite the Nile on Friday, sellers hawked "Intifada" dates and "bin Laden" dates -- the priciest in the market.

"He deserves it," vendor Ahmed Ibrahim, 23, said of the al-Qaeda terrorist chief. The dates come from the southern province of Aswan, reputedly Egypt's best date-growing region.

Ibrahim's allegiance to bin Laden appeared to be at least somewhat in jest, however. He wore a shirt with the name of a U.S. brand.

"This is work," he said pointing at the dates. "This," he said of the shirt, "is my style."

At Al-Azhar, cleric Youssef said the Ramadan tradition of giving political names to dates "does not harm Islam."

But he condemned the holy month's commercialism -- hotels and restaurants trying to cash in by erecting Arab tents for meals, or merchants raising the prices of dried fruits because of high demand.

"These people want to make money out of Ramadan," he said.

The true Ramadan, he said, involved breaking the fast and heading straight to mosque to spend much of the night reciting special Ramadan prayers.

"Going to coffee shops and tents," he said, "this is not the real Islam."