More than 100 of the most prominent members of the Washington area's real estate community were having lunch at the Madison Hotel last month listening to a speech by humorist Art Buchwald.

Though the speech was laced with humor, the tone of the luncheon was serious. Like hundreds of similar lunches and dinners held around the country every year, this was a fund raiser for Israel Bonds. And Buchward's speech had an undertone that recounted the commitment of Jewish people everywhere to the existence of Israel, which turned 30 years old this year.

And after the meal at the Madison, each attendee filled out a small card pledging a bond purchase and passed it to the aisle.

At that lunch alone, Israel sold nearly $1 million worth of bonds, making it a bit easier to understand how Israel Bonds have become the third largest selling security in the United States, behind only stock in American Telephone and Telegraph and United States savings bonds.

An estimated 2 million persons have purchased nearly $4 billion worth of bonds since they first became available in 1951, and 80 percent of the bondholders are in the United States or Canada.

It was almost exactly 27 years ago that David Ben-Gurion, then prime minister of Israel, came to the United States to raise money for his fledgling country. Barely in existence for three years, Israel was overflowing with refugees.

Several Jewish leaders got together and raised the possibility of borrowing from the public by issuing low-interest bonds. The idea was greeted with something less than enthusiam on Wall Street. One leading banker told an early administrator of the bond program that he would be lucky to raise $10 million.

But Ben-Gurion's visit, his first after Israel became a state, resulted in a $51 million sale. Since then, things only got better.

In the first 16 years of sales, $1 billion worth of bonds were sold. During the next five years, another $1 billion were sold. The next billion came in only three years. The fourth billion should be reached in the next few months. Over the years, more than $1.5 billion of bonds have been redeemed.

The money raised by the bonds is earmarked specifically for internal development in Israel. In fact, last year's total of $331 million raised from bond sales made up a full one-third of the entire Israeli internal development budget.

"People buy these bonds first and foremost to help Israel's economy," says the resident of Israel Bonds, Michael Arnon. "They are bought by people who believe in the future of the State of Israel."

To date, 3,100 banks, 1,400 trade unions, 7,770 pension funds, 410 insurance companies, and hundreds of other firms of all kinds also have invested in Israel Bonds. And in a significant departure from recent years, 25 percent of last year's individual investors were not Jewish.

Different types of bonds are available. One version is a 15-year bond that pays 4 percent had is sold in $250 to $10,000 denominations, with a lump sum payment at the end of the 15 years.

A second type is also a 15-year bond, sold in $500 to $25,000 denominations, but it pays interest semiannually. Those two are the most popular bonds among "grass roots buyers," according to an Israel bonds spokesman.

Another set of bonds is sold with a 20-year maturity and 5.5 percent interest on $2,500 to $100,000 notes to predominantly institutional buyers. These have a 90-day liquidity clause.

Another form of bond is a special million-dollar and quarter-million-dollar note that pays a varying interest based on the prime rate. Introduced only two years ago, the million-dollar notes have resulted in sales of $100 million, primarily to banks and insurance companies.

With an international staff of some 900, including offices in every major U.S. city, Israel Bonds uses various types of dinners and lunches as fund raisers - frequently bringing together groups of prominent local insurance, real estate or other industry officials for social functions.

In addition, direct appeals are made through religious organizations and synogogues during the Jewish Holy Day season in the fall.

Without doubt, the largest sums of money are raised during times of direct conflict or war in Israel. Israel bonds had their best year in 1973 - the year of the Yom Kippur war - when slightly more than half a billion dollars worth was sold.

Israeli Prime Minister Menachen Begin's recent visit to the United States did more than promote Israel's 30th anniversary. His speeches in New York, Los Angeles and Chicago resulted in $37 million in bond sales.

While the real estate lunch in Washington was raising $1 million, a fashion show in New York sold another $1 million in bonds.

And this Sunday, Israel Bonds will hold its Ambassador's Ball at the Washington Hilton. Those invited have purchased a minimum of $3,500 in bonds.

Rosalynn Carter will be honorary chairwoman of the ball.