We congratulate Anwar Sadat, who started it all, and Menachem Begin, who responded in kind, for winning the Nobel Peace Price. Egytians may feel Mr. Sadat deserved to win it alone, but splitting it emphasizes that peace involves an interaction and not an initiative alone. Wisely, the Nobel committee cautioned that the prize was given not just to honor what has been done so far but also to spur to completion the process begun in Jerusalem a year ago. Jimmy Carter, we note, got an honorable mention. Americans may be forgiven for thinking that the Egyptian and Israeli leaders would not be Nobel laureates today if President Carter had not drawn their best from them at CampDavid.

Everybody notices that the Nobels happened to be announced on a day when a nasty squabble was goint on. It will pass. But although we remarked on some part of it yesterday, we want to comment on a larger part today. Since Camp David, it seems to us, President Sadat has acted in a manner befitting a recipient of a Nobel Peace Prize. He has carried his own public, swallowed great abuse from other Arab states, and conducted the follow-up peace talks in Washington with discretion and dispatch and without pushing an undue share of his own political burden upon his partner, Prime Minister Begin. His performance has been in the spirit of Camp David.

As for Menachem Begin, he must cope with heavy political opposition - a task demanding courage on political opposition - a task demanding courage on his part and understanding by others. We wonder, though, whether some of us sometimes show a bit too much understanding. The other day Mr. Begin made a gratuitous assertion of Israel's "right" to expand settlements in the West Bank Mr. Begin claimed a requirements to calm his unresconstructed right - a requirement that must be served, but not exaggerated. He also claimed to be angered by some statements made - out of school, he suggested - to Jordan and West Bank Arabs by an assistant secretary of state. He said this although he knows the statement to King Hussein.

Mr. Begin knows further that an Arab summit is about to be held and that Mr. Sadat, who would be criticized there harshly anyway, will be undercut even more by an Israeli gesture that seems to confirm the darkest suspicions about Israel's West Bank design. Even among some Americans, it has to be said, Mr. Begin has raised the question of whether his real policy is not to pocket the Sinai and then to take steps that will render it impossible to tie up the West Bank half of the Camp David package.

We do not share those suspicions. We believe that the forces loosed by Camp David, acting through the procedures laid out there, are virtually sure to produce a West Bank agreement down the road. But history will not unfold by itself. Mr. Begin has an obligation to accept in spirit as well as letter the commitment to a comprehensive settlement made at Camp David. And he must demonstrate his acceptance - most of all to his fellow Nobel laureate.