letter left behind by terrorists who attacked New York and Washington on Sept. 11 contained religious references, inspirational commentary and step-by-step instructions for their suicide missions.

The letter, which officials in Washington said connected the hijackers of three of the four planes, is a puzzling mixture of everyday piety and murderous resolve, according to scholars and Muslim leaders who have read excerpts from it.

The letter speaks of the importance of keeping a knife sharp so as not to "cause the discomfort of those you are killing" and warns against holding prisoners. "Take prisoners and kill them," the letter says. In both cases, the letter says such steps are the way of the prophet.

Some of the letter invokes prayers and uses "very mainstream religious language," John L. Esposito, director of the Center for Muslim- Christian Understanding at Georgetown University, said, referring to excerpts published on Friday.

But, he said, "all of a sudden, after you've read through 90 percent of it, then you get to that set of lines that this is being wrapped around that militant action — "You get your ID's, you're carrying your knives.' "

The four-page letter, released yesterday in the original Arabic by the Justice Department, was found in the luggage of Mohamed Atta, who officials said was on the American Airlines flight that was the first to hit the World Trade Center. The other letters appeared to be photocopies of the one in Mr. Atta's luggage. One was found in the wreckage of the United Airlines flight that crashed in rural Pennsylvania, and the other was found in a car parked at Dulles International Airport that officials said had been used by the hijackers who flew another American plane into the Pentagon.

An F.B.I. official said that in previous cases when agency officials released translations of Arabic documents they had been criticized, and they sought to avoid this by simply releasing the documents without translations.

Attorney General John Ashcroft said the handwritten letter offered "a shocking and disturbing view" into the minds of the terrorists.

The letter's opening sentences, written as a numbered list of injunctions, specify the ways in which the terrorists were to prepare themselves mentally, spiritually and even sartorially for death.

"Pray during the night and be persistent in asking God to give you victory," the letter says. It also reminds the terrorists to bring a suitcase, examine their weapons and make sure their shoes fit well and their socks are straight. It tells them to bless their bodies and their personal effects, like passports, clothes and knives.

Those passages, which carry an ominous weight in light of the acts the terrorists committed, contrast with the more limited excerpts from the letter published on Friday, which were mainly injunctions to pray, along with three common prayers.

"This doesn't sound like someone with a callous disregard for human life," said Imam Talib Abdur-Rashid, spiritual leader of the Mosque of Islamic Brotherhood in Manhattan, after reading through excerpts that dealt largely with the need to pray. "It's very incongruous to me."

A similar opinion was offered by Dr. Faroque Khan, a spokesman for the Islamic Center of Long Island. The excerpts, he said, sounded "like a pep rally for someone going on a very laudable mission" when in fact it was "an evil mission."

"It just doesn't add up," Dr. Kahn said. "The Prophet laid down clear guidelines that, even in the case of a war, you don't harm women and children."

The letter, whose contents were first reported in The Washington Post, also says, "Purify your soul from all unclean things. Completely forget something called `this world.' The time for play is over and the serious time is upon us. How much time have we wasted in our lives? Shouldn't we take advantage of these last hours to offer good deeds and obedience?"

The prayers with which the letter concludes, Dr. Khan said, are common ones, usually used when a person is "facing difficulty or embarking on some important mission." But, Dr. Khan said, the mission undertaken by the hijackers was "totally un-Islamic."

Dr. Esposito said the literate, careful tone of the excerpts suggested that the hijackers had probably begun in society's mainstream, rather than its margins.

"We have a certain need to simply explain what somebody does as totally irrational," Dr. Esposito said. "And therefore the fact that they might be well-educated people and that they might come out of a pious background stuns us."

But, he said, radical movements have often drawn in middle-class people whose convictions led them into violent illegality. Among such people, Dr. Esposito said, were the men who assassinated President Anwar Sadat of Egypt in 1979.

Jane I. Smith, a professor at Hartford Seminary in Connecticut and author of "Islam in America" (Columbia, 1999), described the excerpts as "truly pious."

"Apparently, one can assume what was done was done by people out of a genuine and sincere belief that they were helping bring about the will of God," Professor Smith said. "And that, in turn, may be the most frightening thing about it."