The millenia-old prayers are the same in good times and bad: "Hear, O Israel: the Lord our God, the Lord is one . . ."

But the faithful Jews, this year's celebration of Rosh Hashanah, the Jewish New Year, is the most joyous in ages.

"When Menachem Begin and Anwar Sadat embraced each other in the presence of Jimmy Carter at the end of their historic TV report," said Rabbi Joshua O. Haberman of the Washington Hebrew Congregation, "it was as though a new light had broken through the stormy sky."

The rabbi linked the Camp David peace agreement to the "vision" recorded by the prophet Isaiah: "Arise, shine, for the light has come."

"This new year should be a time of jubliation, of thanksgiving, of hope," he said in his sermon at services on Rosh Hashanah Eve. "For the last 30 years we built Israel, holding in one hand the building trowel and in the other the sword . . .

"Now for the first time in 30 years Israel will be able to build with both hands . . . What unimaginable achievements now become possible! What new dreams become realizable, even the dream of a more perfect society as forseen by the prophets."

The rabbi reminded his congregation that just five years ago on Yom Kipput, which follows Rosh Hashanah by 10 days, "the entire military might of Egypt moved into the Sinai desert south of Israel," while Syria attacked from the north.

"Only a miracle of courage and self-sacrifice saved (Israel) on the memorable Yom Kippur," he recalled, a miracle which he said was fueled by assistance from Jews all over the world. "The unbreakable unity of our people" was "the fire that kept the wolves away in 1973, and throughout 19 centuries of dispersion when oppressed Jewish communities anywhere depended on their more fortunate brothers for their survival."

Now, he said, the accord reached at Camp David has "far-reaching significance for all other world problems. If Israelis and Arabs can come to terms, then no international problem now on the world's agenda is beyond the scope of reason and good will.

"Soviet American detente, nuclear disarmament, even the human rights struggle in Southern Africa and Latin America and behind the Iron Curtain appear to be less hopeless in the light of Camp David."

In the Jewish Calendar, Rosh Hashanah introduces a 10-day period of introspection and repentance ending on Yom Kippur, the holiest day in the year. On Rosh Hashanah, according to tradition, the Book of Life is opened and one's name inscribed, but the Book is not sealed until Yom Kippur.

It is a time, Rabbi Haberman explained to a visitor after the service, in which "we want to measure ourselves against God's justice. If we have fallen short, we have 10 days to make amends" before the Book is closed on Yom Kippur.

Psychologically, he continued, "it is a dramatic accent of the need to forgive and be forgiven . . . it is a profound instrument of introspection."

It is a time when Jews go to synagoguges and temples for the high holy day services. Washington Hebrew Congregation had to schedule four different services - two yesterday morning and two Sunday night, the eve of Rosh Hashanah - to accommodate all the worshipers in its congregation of 2,200 families.

The Rosh Hashanah service includes the kaddish, or special prayers for persons who have died. In his sermon, Rabbi Haberman took note of the death Friday of Pope John Paul I.

"We share with our Roman Catholic neighbors in this community and throughout the world a sense of great loss in the sudden death of their superme spiritual leader who was consecrated only a month ago," he said.

For Orthodox and some Conservative Jews, special Rosh Hashanah onservances will continue through today.