There was no dancing last night at the annual Israel Bonds black-tie ball, a sober reflection of the resurgence of fighting in the Middle East.

"How can we celebrate when mothers in Israel are sitting shiva for their sons that have died . . . ?" said Melvyn Estrin, 1982 Washington campaign chairman for the Israel Bond Organization.

"The gravity of events . . . left nothing to celebrate," said Murry Mendelson, chairman of the ball. It was the second time in the ball's 20-year history that the entertainment and colorful decor have been dropped. A traditionally buoyant and elaborate celebration of Israel's birth in 1948, the festivities were also toned down after the Six-Day War in 1967.

Last night, more than 1,000 people from the Washington Jewish community--including representatives from the administration and Congress--showed up at the Washington Hilton for a simple dinner and a moving show of support for Israel.

But the dinner--exactly one week after Israel's invasion of Lebanon--also proved to be a touchy environment for the politically sensitive.

"No," said Rep. Steny Hoyer (D-Md.), when asked if his presence was meant as a show of political support for Israel's invasion of Lebanon. "I'm here because Murry has a facility in my district," Murry's Steaks Inc. "I don't want to make a judgment, but I understand the rationale behind the invasion."

"We've always been friends with Israel," said Interior Secretary James Watt, offering no further comment on the matter.

Yet to most of the guests, Israel's invasion was absolutely imperative and in the name of peace.

"Israel went in to ensure peace in Lebanon and free the nation of all outside forces--PLO, Syria and Israel," said Abe Pollin, owner of the Washington Bullets and the Washington Capitals. "Now ought to be a time of helping to strengthen the government of Lebanon so as not to allow the PLO Palestine Liberation Organization into that country again."

"The entire northern part of Israel was forced into shelters because of PLO shelling on that part of the state," said Israeli Ambassador Moshe Arens. "We did what any government would have done to protect its citizens and protect its population."

"No other nation in the world would be expected to take the taunting and brutality by the PLO that we have put up with," said Estrin. "Why is Israel expected to take it?"

The evening began with a brief cocktail reception where guests spoke in the somber tones reserved for grave occasions as they mingled around trays of kosher hors d'oeuvres--stuffed mushrooms, pa te', turkey, salmon and fancy fruit.

Among the other guests were D.C. Mayor Marion Barry, Rep. Pat Schroeder (D-Colo.) and Sen. Rudy Boschwitz (Ind. R-Minn.). Washington developer Theodore Lerner, Corcoran Gallery president David Lloyd Kreeger and Pollin were among the evening's sponsors.

The ballroom was stark in comparison with previous years. Plans for thousands of dollars' worth of glittering decorations, a 40-piece orchestra and several Broadway performers were set aside only last Thursday. On the dimly lit stage last night were two flags--American and Israeli. And scattered through the room were several ice sculptures of the Star of David and Lion of Judah.

About 1,000 mailgrams went out Thursday informing ball patrons of the change in events. According to Estrin, the ball picked up considerable support after the change was announced. By yesterday, even the programs had been reprinted.

The Israel Bonds Organization was formed in 1951 to sell securities issued by the Israeli government to aid the nation's economic development. The more than $5 billion raised through the bonds during the last 30 years has never been used for defense.

The ball traditionally is underwritten by about 75 patrons. And although those invited do not pay for tickets, they purchase a minimum of $3,500 worth of bonds annually to be asked to attend.

At the end, everyone stood quietly for the American and Israeli national anthems.

"There are some who say that the number of casualties were small in comparison to the success of the operation," Arens told the crowd a few minutes later, referring to the battles of the past week. "But it was a very heavy toll for us to pay . . . We would have preferred not to have done it at all . . .