"Baruch ata, Adonai . . ."

The cantor led the crowded synagogue in the ancient blessing familiar to Jews, around the world.

But on the platform of the Washington Hebrew Congregation last Friday night, the scene was anything but traditional. Rabbi Joshua Haberman shared a prayer book with an attentive, scholarly man in the long, cream-colored robe of a Muslim imam, or teacher.

On the other side of the massive tablets of the Ten Commandments that dominate the synagogue, another man, garbed in the black, velvet-banded robe of a Presbyterian minister, followed the Reform Jewish prayer book's English translation with equal diligence.

The Sabbath liturgy concluded and stead of the usual sermon, Rabbi Haberman explained that he and the two Rabbi Herman took the pulpit. In-guests - Dr. Muhammad Abdul Rauf of the Islamic Center and the Rev. Dr. George B. Grose, Presbyterian clergy, man from California - would conduct a three-faith dialogue.

While Christian-Jewish conversations have become commonplace in recent years, communication on almost any level between Muslims and Jews is almost nonexistent.

As the host, Rabbi Haberman led off. "The strongest link between us is our belief in God," he pointed out. "The God we believe in is the same God, revered and worshipped by our three monotheistic world faiths."

At the same time, he set the ground rules for the evening. "We are here not to rebuke, not to criticize, not to argue," he said, "but to listen . . . while holding out the hand of friendship."

Dr. Grose, who has pioneered in three-faith dialogues through the Academy of Judaic, Christian and Islamic Studies that he heads in Whittier, Calif., said that to his knowledge the session here was the first time such conversations had taken place within the context of a synagogue worship service.

"The grounds for dialogue," he told the crowded synagogue, "is more than sentiment." In addition to th monotheism the three faiths share, all three groups look to the prophet Abraham as "our father in faith," he said.

He stressed the importance of inter-faith understanding in the light of world tensions today. "Judaism, Christianity and Islam can only be true to themselves when each is in true relationship with their cousins in the faith. The credibility of historic revealed religions is at stake today," he said.

Addressing the senstiive area of Christian missionary activity, Dr. Grose acknowledged that "it is the calling of Christians" to testify to their faith with the objective of attracting others to it.

But he made a distinction between "sharing what we cherish, and conversation." The latter, he said, "is the office of the Holy Spirit, and who are we to arrogate to ourselves what is in God's hand."

He added that for Christians, "it may be that listening to our cousins in faith is a new form of proclamation."

Dr. Rauf, whom Rabbi Haberman introduced as "a scholar and a preacher of his faith and a good neighbor," also took up the theme of amity among the three faiths.

"In this sanctuary we seek to free oursevles from the fears and conflicts that estrange us from one another," he said, in a soft voice that seemed to be subdued by what he said was the "emotion" of the moment.

"The grounds for dialogue between Judaism and Islam are very firm indeed," he said, although he acknoweledged that there has been "some unnatural upheaval which we hope will soon be removed."

Still clutching the Jewish prayer book used earlier in the liturgy, he commented on the similarity between Jewish and Islamic prayers, and concluded his remarks by reading one of the Jewish prayers.

Later Rabbi Haberman said that he had been "delighted" with the exchange and expressed hope that it had prepared a " practical path of cooperation between the Islamic Center and the Jewish community of Wahsington."

For openers, he said, he visualized a "learning interchance" in which members of his congregation might study the Koran of join classes in Arabic at the Islamic Center, and reciprocate with classes in Jewish studies.

"The study area is one for which both sides are ready," Rabbi Haberman said. He also raised the possibility of "visitation of each other's sanctuary."

Rabbi Haberman said his proposals were "just beginnings. Each new contact must give birth to half-a-dozen others. This even has opened lines of communication between Dr. Rauf and myself that we want to widen."