Peace with Israel has so far brought little joy to Egypt.

Three weeks after President Anwar Sadat signed the historic treaty in Washington, the country is beset by economic uncertainty, anxiety about the future and religious unrest.

The economic and political boycott of Egypt imposed by most of the other Arab states is beginning to make itself felt. Even Egyptians who support what Sadat has done express concern over the extent of Egypt's isolation from the Arab world of which it was once the leader.

This is not to say that the country is in turmoil or that the Egyptian people in general are having second thoughts about Sadat's peace policy. The referendum on the treaty to be held Thursday is sure to show that an overwhelming majority of the 10.3 million registered voters endorse it.

But the country is living through a period of anxiety, perhaps invevitable under the circumstances, because it has taken great risks, broken with the Arab world and embraced a histroic enemy but has not yet reaped any rewards.

The promised American economic and military aid is far in the future and the anticipated stimulus to the economy has not had time to develop. Only in late May, when Egypt is to regain a strip of the Sinai coast and the town of EI Arish, will there be tangible gains from the treaty, and even then they will provide new ammunition for Sadat's critics, who accuse him of having made a separate peace.

Egypt has been suspended from the Arab League. Most Arab ambassadors have left Cairo. The national airlines of Syria and Iraq have joined that of Libya in suspending service to Cairo.

Economically, Egypt is apparently going to lose about $400 million a year it has been receiving from the other Arabs as a "confrontation state" in the struggle against Israel. The fate of a comparable amount of largely indirect aid from Saudi Arabia and other states is still unclear.

The Organization of Arab Petroleum Exporting Countries has suspended Egypt, and this, according to economic sources, could lead to a halt in some development projects financed by the organization.

Sadat has not totally escaped public criticm among the Egyptians. While treaty opposition from the left and from Islamic fundamentalists was expected, there has been dissent from other quarters, too. Four former vice presidents, once partners with Sadat in plotting the revolution that ousted the monarchy in 1952, criticized the treaty, as did a respected former minister of education, Hilmy Murad.

Sadat has responded with shrill attacks on his foes at hom and abroad.

Monday he lashed out at the "ignorance, backwardness and emotionalism" of his Arab critics, who he said were playing into the hands of the Israelis. Defending his approach, he argued that the best way to help the Palestinian people is to negotiate with Israel.

In the same speech, Sadat renewed his attacks on Moslem fundamentalist critics in Egypt.

"Some today are exploiting religion," he said. "They want the state to be styled after Khomeini [the Iranian religious leader]. Well, there is nothing easier - summary trials and executions of 10 or 20 people a day."

It was the third straight day in which Sadat issued stern warnings against unrest, religious strife, unauthorized political activity and dissent in the universities.

Sunday he said he had "given orders to the police to shoot on the spot and without any discussion any person attempting to sabotage or destroy state or privately owned properties." The day before he confirmed reports of religious rioting in the upper Egypt town of Assiut, this all contributed to the collective nervousness evident in the security forces deployed at the main squares and buildings of Cairo and the conspicuous movement of troops up to the Libyan border.

Since the signing of the treaty, Egypt has found itself at odds not only with other Arabs but also on accasion with the Irsraelis and the Americans, the sponsors of the treaty and Egypt's only guarantors of its success on the crucial Palestinian issue.

Prime Minister Mustafa Khalil complained to the Americans about the understanding between them and the Israelis over how the United States would respond if Egypt violated the treaty.

As for the Israelis, Egyptian officials say that public statements of Israeli leaders about their vision of Palestinian autonomy and Israel's expressed intention to push ahead with settlements in the West Bank are unnecessarily compounding Egypt's difficulty in selling the treaty to the other Arabs, particularly the Palestinians.

Presidential adviser Sayed Marei, talking Friday on Israeli television, suggested that Egyptian and Israeli leaders alike "refrain from speeches and public declarations." In the Egyptian view, Israel's insistence on maximizing its advantage on every point and flaunting its gains in the treaty ensure that the Palestinians, Syrians and Jordanians will stay out of the future negotiations.

Privately, Egyptian officials concede that not all the balme for Arab rejection fo the treaty can be laid at the feet of the Israelis.

"Sadat himself failed to deal effectively with the other Arabs after Camp David," said a prominent official who deals with other Arab diplomats here. "It was a serious mistake to let the Americans take on the job of selling it to the other Arabs and for Sadat to resort to self-righteousness."

He and other Egyptian officials conceded that this country will be in an embassassing and perhaps dangerous position if in six months or a year, when the Israeli flag is flying over an embassy in Cairo and the borders between the two countries are open, there has been insufficient progress on the definition of Palestinian autonomy for any other Arabs to be enticed into the negotiations.

"I don't even want to think about it," a Foreign Ministry source said. "This is what really matters, the political development, not the economic sanctions. Right now, with all the Arabs united against us, I would say there is no chance to get any Palestinians at all, any, into these negotiations without a direct American approach to the Palestine Liberation Organization."

"This was badly mishandled at Camp David with the PLO and with Jordan," said another. "Now the best thing for the U.S. is to approach the PLO because the Palestinians are the only ones besides us with a vested interest in changing the status quo in the occupied territories."

President Carter has offer to "immediately start working directly" with the PLO, but only if the PLO accepts U.N. resolutions implying acceptance of Israel's right to exist, which it has so far refused to do.

Judging by Arab reaction of Baghdad, the treaty's close identifaction with Washington has induced many Arabs conscious of their Third-World and revolutionary connections to spurn it, a reaction Sadat failed to anticipate.

Sadat has been counting on the implementation of the treaty and the gradual acceptance of it as an accomplished fact to bring some other Arabs to his point of view, or at least to the point where they will enter the negotiations to see for themselves.

It is still too early to tell whether his judgment will be validated, but at the moment, Egyptians concede, there is little cause for optimism.