In the end, they sang, some 600 men in dark suits and hats, as they stood facing the president of the United States and the prime minister of Israel amid the tulips on the soft, green lawn that slopes down from the White House toward the Jefferson Memorial in the distance.

It was a little cool but otherwise perfect, brilliantly clear spring day that made the snow of February and the approaching heat of August seem remote. It was a day when the horrors of the past could be recalled, if only to resolve that they never be repeated, but also a day when courtesy and good taste dictated that the differences of the present go unmentioned.

So they sang, first in Hebrew, the words of the "Hatikva," which means "The Hope" and is the Israeli national anthem, and then the familiar English words of Francis Scott Key in "The Star-Spangled Banner."

It was emotional and seemed spontaneous, a gesture of unity between two nations that have always been friends and a fitting climax to the brief meeting yesterday between the leaders of those nations, Menachem Begin and Jimmy Carter.

These are not the best of times in the 30-year history of American-Israeli relations. In Washington, there is a feeling among some that Begin, survivor of the Holocaust and former Israeli freedom fighter, is impeding progress toward a Middle East peace settlement. In Jerusalem and among Israel's strongest supporters in Congress, there is fear and anger over Carter's insistence on supplying war planes to Saudi Arabia. A parliamentary clash between these forces, the Carter administration and the "Israeli lobby," is unfolding on Capitol Hill.

But diplomacy being what it is yesterday's symbolic and largely ceremonial meeting was probably inevitable Begin is in the United States for a week-long speaking tour to commemorate the founding of the nation of Israel. In all that time, it would seem odd, if not insulting for the president not to ask to see him.

So just before 1:30 p.m. yesterday, the long, black limousine bearing Begin swung through the northwest gate of the White House and up the drive way lined by a military honor guard as the trumpeters played a fanfare. Waiting to greet him at the entrance to the White House West Wing was a broadly grinning Zbigniew Brzezinski, the national security affairs adviser who has been blamed by some pro-Israeli leaders for what they consider to be an administration drift toward the Arab states and away from Israel.

On the other side of the building, the day's guests were gathering. About 1,200 Jewish leaders, most of them rabbis, had been hurriedly invited for a reception on the South Lawn to mark the founding of IsraeL. About 600 showed up.

They trudged along the driveway that arcs behind the White House - a long, drab line of men and a handful of women, to take their places on the lawn in front of the podium where the two leaders would speak.

As the guests sipped coffee and punch, Avraham Weiss, an intense, young rabbi from Riverdale, N.Y., began handing out copied of a letter he had written to Carter. It opposed, in polite language, the proposed sales of warplanes to Saudi Arabia and Egypt.

Their 30-minute meeting over, the president and the prime minister appeared on the lawn.

Carter spoke first, in moving terms about "the ultimate in man's inhumanity to man, the Holocaust" of World War II. The 6 million Jews killed by the Nazis, he said, died in part "because the entire world turned its back on them." He vowed, as have the Israelis, never to allow such a horror again.

Then, in one of those symbolic gestures he is known for, the president announced that he was appointing a commission to recommend to him an official American memorial to the victims of the Holocaust.

"For 30 years, we have stood at the side of the proud and independent nation of Israel," Carter concluded. "I can say without reservation . . . that we will continue to do so not just for another 30 years, but forever."

When it was Begin's turn to speak, the crowd broke into song again, chanting the words of "Am Israel Chai - The People of Israel Live." The prime minister stood mute at the podium, staring at the faces before him.

Begin spoke of Israel's determination, of the long, bitter struggle of the Jewish people, first for survival and then for freedom. And, like Carter, he spoke emotionally of friendship between allies.

"There is that feeling that America and Israel, are inseparable, friends and allies," he said.

After some mingling on the lawn, it was quickly over. Begin had a plane to catch to continue his speaking tour last night in Los Angeles. Carter had business waiting for him in the Oval Office.

Later in the afternoon, Begin's motorcade flashed passed the White House one last time. His limous