ITT WAS three years ago this month that Andrei

Sakharov was grabbed on a snowy Moscow street by the KGB, brought to the office of the state prosecutor, and summarily informed that he was being exiled to the provincial town of Gorki. For good measure, the authorities told him that all his awards and prizes had been rescinded.

The purpose of the action was brutally simple: to silence the great physicist and human rights activist by denying him access to those needing him the most--the political dissidents whose spokesman he had become--and to those supporters in the West for whom he was (and is) a unique symbol of dignity and defiance.

In a way the Soviet ploy worked. After a brief uproar of protest at home and abroad, the Sakharov case was duly entered on the lengthening list of grievances harbored against the Soviets--Afghanistan, Poland, the arms buildup and the continuing repression of dissent. As with so many other Kremlin misdeeds, the Soviets proved unyielding on letting Sakharov return home

As the weeks of exile turned into months and years, the quiet voice with the slight lisp seemed if not stilled then muted by the Gorki muzzle.

That is what makes On Sakharov (edited by Alexander Babyonyshev, a recent, young Soviet ,emigr,e now living in Boston) welcome and necessary. The book is a decisive demonstration of the continuing strengths of Sakharov and of the idealism he espouses and epitomizes.

The contents of the work is a m,elange of varying literary and docmentary merit. There is a collection of anecdotal tributes and declarations, mainly from other dissidents, meant to remind us how important Sakharov is and why. There are also a number of essays devoted to Sakharov's scientific career. A chronology of his life is helpful and he offers a brief autobiographical introduction which leaves me eager for a full-fledged memoir.

But the most moving passages are from the stream of Sakharov's letters and statements that have poured forth from Gorki and been sent from the Soviet Union by others with some difficulty and risk. They are the vivid proof that Sakharov endures. They are the testimonials to his commitment to individual liberty, a conviction that transcends categories of left and right. His attitudes are not just a reflex against Soviet depredations; he is a philosophical humanist of broad range.

"The ideology of human rights," he wrote in 1980, "is probably the only one which can be combined with such diverse ideologies as communism, social democracy, religion, technocracy, and those ideologies which may be described as national and indigenous. It can also serve as a foothold for those who do not wish to be aligned with theoretical intricacies and dogmas and who have tired of the abundance of ideologies, none of which have brought mankind simple happiness.

"The defense of human rights is a clear path towards the unification of people in our turbulent world and a path toward the relief of suffering."

Yet Sakharov is not merely a rhetorician, although in Gorki he is without an audience that might applaud his actions. (Interspersed throughout his entries are chilling hints of security police actions to cut him off from friends and reporters.) Despite uncertain health and his age, 61, Sakharov and his beloved, resolute wife Elena Bonner went on a prolonged hunger strike in the fall of 1981 aimed at forcing the Soviets to grant their daughter-in-law an exit visa so she could join her husband in the United States. It is hard to imagine an isolation greater than that of self-starvation in what amounts to KGB detention.

Personal details of their ordeal are not included in the book. But when, remarkably, the Soviets gave in after three weeks, Sakharov found exactly the right send-off for the young woman in the words of Yugoslav dissident Mihajlo Mihajlov: "Motherland is neither a geographical nor a national concept," he recalled from his hospital bed in Gorki, "Motherland is freedom."

Of considerable topical interest are Sakharovk's views on the arms-control issues that are at the forefront of East-West relations. Sakharov is for multilateral disarmament and the eventual banning of all nuclear weapons. But he believes that a prerequisite is an arms-parity between the superpowers that takes account of all the political, psychological and geographical factors involved.

What that means to the Reagan administration --and to the Andropov regime--is that no real arms reductions are possible until the superpowers agree to accept genuine equality. By a long shot that has not happened. As I understand Sakharov's views, he believes all the haggling over weapons is pointless if significant sentiment exists on either side that the other is poised for superiority.

Only in circumstances of mutual trust and with a balance of forces between the contesting nations, he writes, "can there be progress in reducing conventional and nuclear weapons and reducing the danger of war. Under those conditions, it will be possible to take the exceedingly important step toward removing the threat of thermonuclear annihilation from mankind. That step would be taken by concluding a treaty against any first use of nuclear weapons."

That sounds like a wildly unrealistic goal, given the contemporary reality, the suspicions and political pressures which drive Washington and Moscow to ever more massive outlays for defense. How naive the notion undoubtedly seems. Trust? Balance?

But then, Sakharov is the sort of fellow who believes he can do what others dare not try. A man prepared to challenge Soviet power even after he is punished for doing so. On Sakharov is a book about the best instincts of courage and compassion mankind has to offer.