On Friday, Oct. 21, 1983, Navy chaplain Arnold Resnicoff was in Beirut to conduct a memorial service for a Jewish marine. He stayed another day, because rabbis don't travel on the Sabbath.

At 6:20 Sunday morning he was standing 100 yards away when a bomb obliterated the Marine barracks, killing 241 soldiers. He was, he says, "one of two chaplains left standing."

A few days later President Reagan asked him to recount his feelings. He wrote: "If the world had more interfaith foxholes, maybe we wouldn't need foxholes at all." Reagan read the letter to the Baptist Fundamentalist '84 Convention.

This week Lt. Cmdr. Resnicoff, born in Washington and raised in Hyattsville, was hastily dispatched to Iceland to conduct services for Jewish officials and reporters accompanying President Reagan to the summit with Mikhail Gorbachev. Yom Kippur, the Day of Atonement, the holiest day of the Jewish year, begins at sundown Sunday.

The timing of the summit is troubling to some Jews. Bernard Kalb, who resigned Wednesday as State Department spokesman, said he would not have gone to Reykjavik because of Yom Kippur. Reporters Daniel Schorr of National Public Radio and Barry Schweid of the Associated Press have decided not to attend.

"What is President Reagan going to do on Yom Kippur, talk to Gorbachev about Soviet Jews?" Schorr said. "I have to question the appropriateness of him having picked the date."

"The return is on Sunday," said Assistant Secretary of Defense Richard Perle. "And it's before sundown."

Resnicoff thought about the timing, too, and says it would have been "a positive statement in support of Jews" had the administration lobbied for other dates.

"I thought about it briefly," he said. "Not that it is evil or wrong, but unfortunate.

"My mind changed, though, and I thought how appropriate it was. On the High Holy Days, we think about the idea that we have to make a decision as individuals, and as nations, whether to repeat old cycles or break out of them, or with a new year, whether to go in a new direction. I thought, 'How wonderful that at this time, when the two most influential men in the world are meeting, Jews around the world are praying for just such events.' "

Resnicoff will offer Sabbath services in Iceland tonight (his 40th birthday), and Yom Kippur services on Sunday and Monday. Yom Kippur begins a few hours after Reagan is scheduled to return to the United States.

Raymond Dressler, administrative assistant to the Navy chief of chaplains, said Resnicoff was picked to go to the summit last Friday after the office received an inquiry from the White House about the availability of services in Iceland. There were none.

"My suspicion," Resnicoff said, "is that I happened to be available. It's hard to find a rabbi in the world that doesn't have a job for Yom Kippur."

He never thought he'd be a rabbi. Rabbis had twinkling eyes and long white beards. His grandfather and his great-grandfather were rabbis in Russia. Later his grandfather emigrated to the United States, in search of religious freedom. He remembers visiting his grandfather's congregation in Brooklyn and thinking, "You had to be born to be a rabbi."

He had been bar mitzvahed but he was not, he says wryly, "a ritually observant Jew."

Then he went to Vietnam. He was a naval officer aboard an old World War II ship, hauled out of mothballs to patrol the Mekong Delta. As an officer, he listened to sailors who shared their anger and fear. As a Jewish officer, he was prevailed upon by Protestant chaplain Les Westling to conduct services as a Jewish lay leader. The idea of combining "faith and kindness" as a profession began to appeal to him. Westling, an Episcopal priest, encouraged him to consider the rabbinate.

"I'm probably the only one in the history of the Jewish Theological Seminary," Resnicoff said, "to get in not with a letter saying I'm a good Jewish boy, but with a letter from a Protestant chaplain." He graduated in 1976.

There was a stint in Japan and later in Norfolk, where he became involved in the movement to establish the Vietnam Veterans Memorial. He delivered the closing prayer at the dedication ceremonies. "I prayed there when no one came and when 200,000 came," he said.

Resnicoff is currently assigned to the Naval Chaplains School in Newport, R.I., where he lives with his wife and daughter. He helps new chaplains adjust to military ministry. He also teaches a course at the Naval War College called "Faith and Force: Religion, War, and Peace," which is, he says, "about fighting back without losing our values."

He says he has struggled with the internal conflict between his faith and his military allegiance and that "I continue to struggle.

"We have a term that we teach new chaplains -- 'marginality,' " he said. "We teach that if a chaplain is absolutely uncomfortable with being in uniform, with the system, the chaplain corps is not for him. We also teach that if the chaplain is absolutely comfortable with his uniform and the system, then it's also probably not the place for him. You should be uncomfortable with the idea of violence and yet believe, not just as a matter of rhetoric, that the military is a force for peace."

He has been thinking about the sermons he will offer in Iceland. He says he will talk about "an idea I see in the Yom Kippur liturgy, the challenge of living in a world of dreams without falling into the trap of living in a dream world. There is that famous quote from Isaiah that everyone knows about beating swords into plowshares. But Joel says just the opposite, that we should beat plowshares into swords.

"I want to talk about the idea that we have to dream about the day we can lay down our plowshares, but that day may not be here yet."

Before he left, someone asked what he would like to tell Gorbachev. "I said, 'All I have to do is stand in my U.S. Navy uniform with the Ten Commandments on the sleeve.' My presence and the uniform I wear talks about how a nation can be strong and believe in the rights of all people to religious freedom."

He sighed. "I'm a really corny guy," he said. "I'm not just corny in sermons."