The preacher has a vision: The Palestinians marching from the Lebanese village of Nabatiyeh to the Israili border -- marching back home.

"Supposing they had 100,000 refugees marching to Zion -- no bombs, no guns, saying they're marching home. They could sing that hymn, 'Marching to Zion.' They'd get turned back. But wouldn't you join in a march like that? I think that would touch the conscience of the world.There are Jews who would march with them."

Rev. Joseph Lowery, president of the Southern Christian Leadership Conference, sits back, arms outstretched, one leg hooked on the arm of the cushioned chair. He envisions something like the marches through the South with Martin Luther King and the SCLC. "Well, we didn't mention it yet," says Lowery, who just returned Friday from talks with Palestine Liberation Organization leader Yasser Arafat. "That's the next step."

He is up on his feet. "Palestinians are not trying to say [to the Israilis], 'We want your land'; they're saying, 'We want to live side by side with you.' Arafat said they could all live in occupied Palestine with a Jewish president -- well," he interrupts himself, "maybe he wanted a Palestinian prime minister . . ." He trails off, chuckling. But back to the march.

"They could sing a song black folks sing -- 'On Jordan's stormy banks I stand and cast a wishful eye, to Canaan's fair and happy land where my possessions lie . . . '"

His voice is a deep-throated whisper. In his Mayflower Hotel room, the TV 6 o'clock news is playing soundlessly.

"'O-oh who will come and go with me? I'm bound for the promised land,'" he sings softly, smiling, wide-eyed. He settles back into his seat, hands clasped, his foot gently tapping out the rhythm on the carpeted floor. "'I a-am bound for the promised land, I a-am bound for the promised land. O-oh, who will come and go with me? I'm bound for the promised land.'"

Lowery has just returned from a five-day peace-seeking visit to Lebanon. Slipping into Washington for the Congressional Black Caucus' annual meeting last weekend, he talked happily of being tired from his trip. He cracked jokes about suffering from jet lag. Saturday, he and D.C. Del. Walter E. Fauntroy, chairman of SCLC's board, held a press conference to pronounce their mission last week to get the PLO to consider a "moratoriam on violence" a success. They have even asked Arafat to speak at the first of a series of educational meetings across the country on the Middle East.

It's part of the SCLC's foray into the complex and sticky arena of Middle East problems, prompted barely a month ago by U.N. Ambassador Andrew Young's forced resignation after his unauthorized meeting with a PLO representative.

"We are not negotiators. We are messengers," Lowery said. "Whether Arafat says yes or no [To the proposed moratorium on violence], we consider ourselves successful. We're not going to draw any lines on the map. The groups should be brought to the table."

So the SCLC has trod where secretaries of state and heads of state have not, because, said Lowery, "we feel God is directing us."

And in the process, they have raised the ire of the most powerful Jewish groups in the country -- people who do not make a habit of talking to the PLO, the bitter enemy in the struggle for land and homeland.

A snag developed in Lowery's peace mission -- Israeli Prime Minister Menachem Begin refused to meet with the 10-man delegation of black leaders. "First the [Israeli] embassy said it was because of the holidays," said Lowery. But he is undaunted. "In the long run I think thoughtful Jewish people committed to peace will all understand what we're doing."

Lowery and the other leaders met with Arafat in his office. "I expected a mean, brutal, gruff and rough fellow," said Lowery. "In fact, he's a very charming fellow -- very informed, intelligent, an engineer by vocation. He gave us a history of the struggle. He started out softly, and then when he warmed to his task, he got emotional."

Lowery said he saw suffering in Lebanon -- homes for orphaned children, bomb-ravaged parts of southern Lebanon that looked as bad as villages in Vietnam. "Arafat talked about the people -- they have problems getting birth certificates, death certificates, passports."

He would not say whether he considers Arafat a terrorist. "How do you define terror?" he asked.

Lowery met with the Phalangists, the Christian Party, enemies of the PLO. "The PLO didn't want us to meet with them, but we did. There's a line between East Beirut and West Beirut, and we crossed it. Even the Syrians (peace-keeping forces) can't go across. But we did. We went to the Phalangists and preached the same gospel. They agreed to consider a moratorium on fighting if the PLO did."

He met with Arafat for 3 1/2 hours, he said. "When we talked about the moratorium on violence at first he was rather . . . uh . . . adamant. They had to defend their homeland, Arafat said. They feel they've been banished from their homeland. They're fighting to regain it. We told them we support the rights of the Palistinians and of the Israelis. We said, 'You should recognize the nation of Israel without boundaries.' He said, 'You don't know what you're asking.'

"He got up and walked around. He seemed to be agonizing."

They talked more. "Arafat said, 'We will take the proposal [of moratorium] to our executive council and we will give you our answer in a week.' And then we jumbed up and shouted. We rejoiced.

"We asked Dr. Harry Gibson of the United Methodist Church to pray. Then a Roman Catholic priest said a prayer in Arabic. And we wept. And at the end of the prayer, someone -- I don't know who -- started singing 'We Shall Overcome' and Arafat just immediately crossed his arms and linked hands.

"It was kind of strange," said Lowery. "We were singing with an added dimension. Usually we sing that song about domestic issues. But we were 1,000 miles from home -- singing with these strange people."

The song that led Martin Luther King and his followers through the most brutal of struggles: Just what is Joseph Lowery doing singing it in the Middle East?

"You want it chapter and verse?" asked Lowery, smiling. He has been assailed with that question from all sides for the past month. He has an answer:

"'Go there ye forth, into all the world and preach the Gospel.' That's the mandate." He turned to Al Sampson, an SCLC official who had sat quietly through the interview. "Get the Bible, Al, and look it up. We take 'all the world' to mean the District of Columbia, Birmingham and Beirut, Dublin and Detroit.

"When SCLC got involved in the Vietnam War, we were highly criticized. People said, stay in civil-rights issues, blacks don't know anything about foreign policy.But we're affected. Blacks died disproporitonately in the Vietnam War. If we have another war, blacks will die."

Then there is the impact on the American economy: "When we met with President Carter last December," said Lowery, "he proposed drastically cutting domestic programs while raising the defense budget $10 billion. A lot of our money is being spent to support the Israeli defense fund. So we can't spend more on housing and unemployment.

"The goal of SCLC has always been to seek justice and social change through nonviolent means. It has always been to support human rights for all people. We think what we're doing is consistent."

Sampson appeared with a Bible, and the two paged through it. "Matthew 28:19 and 20," Lowery said. The mandate.

Lowery, 54, is friendly, relaxed, with an air of authority lent by his three-piece suit and the deep, double furrow etched in his forehead.

He helped lead early civil-rights battles in Alabama and Tennessee and was one of the founders of the SCLC 22 years ago. In 1977, SCLC delegates elected him president. He is still the pastor of the Central United Methodist Church in Atlanta.

The golden days of the SCLC, when Martin Luther King was alive, are gone now. The money is scarce, the attention sporadic.

We always been broke," he said, smiling ruefully and slipping into the vernacular. "All civil-rights organizations have had problems raising money. People thought the civil-rights movement was dead. They thought we'd solved all the problems," he said, looking up in mock-seriousness. "Black unemployment is high, black median income has slipped since the early '70s."

The SCLC has marched in Decatur, Ala., twice this year -- to highlight poverty and unemployment as well as the case of a young, black, retarded man convicted of raping a white woman in Alabama. Both times the Ku Klux Klan also marched, and the first time several people were shot.

The SCLC has not gotten any money from Palestinians, Lowery said. "If they did contribute, they didn't write Palestinion on the check," he quipped. "We're not seeking any money from any Arab sources."

Martin Luther King 222 was among the 1,000 who came to hear Lowery's group report on the Middle East mission at the Canaan Baptist Church in Harlem, said Lowery. "He said to me, 'Uncle Joe, some people jump up and shout when they are deeply moved in church. When I'm deeply moved, I cry. Tonight, I cried. Uncle Joe, I think Daddy would be proud.'"

Al Sampson spoke up. "And afterwards Dr. Lowery said to him, 'Marty, there are a lot of things that people want in life, but this is one of the greatest things that I've gotten in life.'"

Lowery listened with his eyes closed, head back. He opened his eyes and smiled. "I'd like to think Martin's pleased." He leaned forward, his voice growing stronger. "All we've asked for is peace and justice. Why should calling for peace and justice infuriate people? We've said to Arafat, 'Do not put any more bombs in garbage cans' -- where's that part about the sword?"

Sampson brought him the Bible again.

"Matthew 13:3. 'Behold a sower went forth to sow. Now some of the seeds fell on stony places . . . '" Lowery read on. "'But others fell in the good ground and brought forth fruit.' Now we can't guarantee this, but we've sown the seed."