"When you have a diamond, you don't treat it like glass." That's how Judge William Beasley Harris, who died last week at 70, would explain privately how he could live happily in the shadow of the career of his extraordinary wife, Patricia Roberts Harris, 59, the former Carter administration cabinet member, diplomat and District mayoral candidate.

But even so eloquent a testimonial of love falls short of telling precisely how he could so graciously grant her the spotlight and lead the offstage applause. He was married to a woman whose record of achievement has been matched by a select few. She served as secretary of Health and Human Services and secretary of Housing and Urban Development. When Patricia Harris became U.S. ambassador to Luxembourg, her husband left his law practice to accompany her.

In a city characterized by power, money and staggering egos, he was one of those rare and special men to whom we owe a debt we would feel awkward expressing. Yet without the personal support that such men provide their wives, some women whom we admire would be less free to serve. For blacks in public life, that need for personal support is particularly acute.

The secret to Bill Harris' support of his wife, friends say, was a deep personal security and strength emanating from a well-defined sense of his self-worth, his wisdom and love of life, and his sure knowledge of his wife's love and appreciation in return.

Bill Harris worked his way through college and law school waiting tables, like many black middle-class men of his and later generations. And although his professional life included practicing law, training hundreds of black lawyers at Howard University, serving as legal consultant to the State Department and spending the past 10 years as an administrative law judge with the Federal Maritime Commission, he used his off-duty time as an advocate for the young and poor in civic and volunteer activities.

"He was a member of a 29-year marriage partnership dedicated to public service," his friend Vernon Jordan said in eulogizing Harris last Friday at the Washington Cathedral. But the private part of the Harrises' life together was extraordinary, as well.

"He was her most loyal, enthusiastic and dedicated supporter," said Jordan. "He was there, he was her anchor. . . . Oh, what a marriage."

Another friend, Charles Ebbecke declared: "He could stand confidently in the shadows, completely unthreatened when the spotlight fell on Pat, and he felt an inestimable joy on where that spotlight fell. His strength was so rooted in his values that there wasn't much that impressed him. He was his own man, unmoved by titles, wealth or fleeting power."

Only meeting and shaking hands with the Pope moved him to "delay washing that hand," said Ebbecke.

During the mayoral campaign, an aide recalled of Harris, "he would have the dinner ready and actually get pleasure out of it. He served her breakfast in bed. In 1974, Pat Harris received two write-in votes for mayor. Bill's was one of them. He received joy out of her rise. That strength helped her to keep advancing."

Harris cared for his wife because he could care for others, and he shared her understanding of a black community strategy holding that educated blacks had a duty of service to their community that was central to their professional lives and includes reaching out to those still aspiring to middle-class status.

"He treated you as an equal," said Lloyd Logan, 29, chauffeur and bodyguard for Pat Harris during her turbulent and unsuccessful race for mayor in 1982. "He was full of life and joy and was always ready to tell a story or joke. He didn't have to prove to himself or others that he was a man, because he knew that. Here was his wife excelling beyond him and she needed support from her husband. He gave it to her willingly."

The debt to Harris, in Logan's case, was quite specific, a lasting legacy.

"It helped me a lot as a young black man to watch their relationship," Logan said. "Most males my age are out to get theirs and only theirs. For a relationship to work, I saw that there has to be trust first, compatibility and respect.

"It is so hard to make a black relationship work today. Men don't know how to deal with women and don't know who they are, so they are constantly trying to prove to themselves and their cohorts that they are a man. Watching him showed me how to have a lot more patience and understanding in dealing with women and how to be sensitive to their wants, needs and desires."