It was not your ordinary Sabbath service at Washington Hebrew Congregation last night.

A gospel rock combo played Israeli songs and nondenominational hymns with a finger-snapping beat, and on the platform, Christian ministers in business suits and cowboy boots were intermingled with the synagogue's rabbis and cantor in their flowing black robes and fringed white prayer shawls.

" 'This is the day that the Lord hath made . . . ,' " Rabbi Joshua Haberman began the familiar scripture in his welcome to the worshippers. A rumble of "amens" interrupted him.

Last night's service was billed as an evangelical-Jewish solidarity Sabbath service. There have been several interfaith services involving Jews and liberal Protestants and Catholics, but last night's gathering is believed to be the first time that Jews and conservative evangelical Protestants have worshipped together on the east coast.

Jews have traditionally been alienated by aggressive evangelistic tactics that are characteristic of conservative evangelicals. But in recent months as their former liberal Christian allies have grown increasingly critical of Israel, Jews have turned to the conservative evangelicals.

Dr. Paige Patterson, president of the Criswell Center for Biblical Studies in Dallas, told last night's congregation that evangelicals are moved to make a new alliance with Jewish groups "because of our interest in prophecy."

He explained that "evangelicals have an interest in Israel because we believe what we see today is a fulfillment of the prophecy" that Israel must be reestablished as a state before Christ's return to earth.

Rabbi Haberman told the congregation that "the time has come for Jews and evangelical Christians to come together on the common spiritual ground that makes all of us the children of God."

He called last night's joint service "a truly historic milestone in Jewish-Christian fellowship and brotherhood." He drew applause and hallelujahs when he said: "Let's press forward on the job for which God has chosen us."

After the service the Jews and Christians adopted by acclamation a declaration calling "the restoration of Israel to its Biblical homeland the further unfolding of God's plan."