THE ISRAELI government, eyeing the PLO buildup and the Syrian presence in Lebanon, had been looking for an occasion to hit, and it would have been extraordinary if it had not found one. In the event, the occasion was provided by the killing of two Israelis abroad, a diplomat who was shot in Paris and a soldier whose jeep was blown up in a section of southern Lebanon in effect occupied by Israel. The Israeli air force responded, as usual hitting some military targets and some civilians. As night fell, the question was whether Israel would consider that it had adequately shown its steel, and whether the PLO and perhaps Syria would feel compelled to retaliate. The United States was urging restraint.

This is a difficult moment for Israel. It is uprooting, in great pain, thousands of its settlers and preparing to yield up the last slice of Sinai by midnight on Sunday for a peace with Egypt whose content must remain uncertain at best for a very long time. In the West Bank and Gaza it faces a Palestinian nationalist movement that it cannot conceivably succeed in suppressing; its very effort strains its relations with numerous countries, even friends like the United States. Across the Lebanese border sits a PLO army in a position and perhaps of a mind to do considerable harm. Syria's forces in Lebanon are also substantial and dangerous.

In these circumstances, it is not surprising that the Israeli government should be in a frightened, prickly and somewhat reckless mood and that it should be demanding from both Egypt and the United States assurances that they mean to stick to their respective commitments to Israel. The Israeli military action on Wednesday, a taste of the Begin government's dream of breaking the back of the PLO's armed forces, can be considered as a certain test of Egyptian and American constancy.

So this is not the moment for sermons to Israel. It is a moment for respect for Israel's anguish--and for mourning the latest victims of Israeli-Palestinian hostility. It is a moment to hope that the cease- fire across the Lebanese border holds.