MENACHEM BEGIN'S success in gaining the Israeli parliament's approval of the Camp David package represented awesome leadership. By subordinating some of his own most fundamental convictions and splitting his political base in the process, he made plain that he is dead serious about peace. He could not have demonstrated more effectively that Anwar Sadat, in initiating the process of peace with Israel, took risks wisely and well.

Recall that immediately after the summit Mr. Begin said he would not enforce party discipline or otherwise bring his personal influence to bear on the Knesset vote on the requirement, agreed on at Camp David, that Israel dismantle its post-1967 Sinai settlements before Egypt would sit down to write a peace treaty. His seeming diffidence puzzled many people, here as in Isreal: How could he fail to do what was necessary to support his own agreement, one promising Israel nothing less than its first taste of peace?

The answer, we think, lies in the fact that Zionism, in the form most universally held and deeply felt among secular Israelis as well as religious ones, means settling, pioneering, sacrificing, redeeming the Jewish homeland by building a new life. It is precisely that passion that has led many Arabs to believe over the years that the essence of Zionism is expansionism: Never had a Jewish settlement been voluntarily removed. Mr Begin is in this sense as passionate a Zionist as anyone in his country. Evidently, he could not easily bring himself to swallow his passion, to support dismantling the settlements in Sinai, and to take the political heat - especially the heat coming with special intensity from his oldest friends and closest political allies.

When Mr. Begin found he actually could not count on a majority within his own Likud bloc, however, he switched course. He accepted the fact that repudiation by his own supporters would undercut both his prestige and his diplomacy, and he threw himself into battle, finally warning that he would resign if Likud did not back him. He had to counter a good deal more than charges of "anti-Zionism" on the settlements issue. He had also to meet pervasive fears that in the "framework" affecting Egypt he had gravely jeopardized Israel's security and in the framwork affecting the West Bank he had virtually invited establishment of a hostile Palestinian state.

In the end, after 17 unbroken hours of debate, the prime minister won overall as expected, 84 to 19. The vote was agonizing even for those who supported the government, and it provided a true test of the relative value that Israelis place on settlements and peace. But Mr. Begin split the Likud, which went with him only by 28 to 19. In the Herut party within Likud - Mr. Begin himself founded Herut - only 11 of 24 members supported him.

The Knesset debate should lead promptly, as Jimmy Carter said yesterday, to an Egyptian-Israeli peace treaty. That is the point of the exercise. The debate should also lead to a tempering of the impatience still widely felt toward Menachem Begin, by an appreciation of the ruggedness of the political terrain he must traverse on the way to peace. Mr. Carter set a certain example yesterday, abandoning the combative tone in which he had earlier discussed his differences with Mr. Begin over future West Bank settlements and granting that those differences involved misunderstandings that own anxieties about Mr. Begin, but if his performance in the Knesset debate is typical of his approach from here on in, those anxieties will be a thing of the past.