Pope John Paul II'S order that priests not hold public office reflects the pope's strong convictions that political position and priesthood are not compatible, church sources here reported today.

The pope has told associates that social or political activism is not a priest's proper role, these sources said.

Yesterday the pope told priests in Kinshasa, Zaire, "to leave political responsibilities to those whose concern they are. You have another role, a magnificent role, you are leaders in another sector."

"Your domain of action, and it is vast, is that of faith and morals," he added.

The Rev. Robert Drinan, who represents Massachussetts as a Democrat in the House of Representatives, announced today that he will not seek reelection after he received directive from his superiors in the Vatican reflecting the pope's wish. Other American Catholic clergy have also been informed of the directive.

The pope's opposition to social activism among priests also emerged recently in his lukewarm reactions to the murder of Salvador's crusading archbishop, Oscar Arnulfo Romero. The pontiff's initial response to the March 24 assassination criticized the violence but was short on praise for the slain archbishop. His strongest words of appreciation for Romero came 10 days after the assassination at a Vatican general audience.

The present code of canon law, currently in the process of revision, dates back to 1918 and rules out elective office without approval by the local bishop. The 1971 Bishops' Synod in Rome dealing with the priesthood also left it up to the local bishop to determine if secular activity in general served the mission of the church and other Christians and was thus compatible with the priestly ministry.

The synod also decided that "leadership or active militancy on behalf of any political party is to be excluded by every priest unless in concrete and exceptional circumstances this is truly required by the good of the community and has received the consent of the bishop."

Over the years a number of priests have engaged in various sorts of political activity, with or without the approval of their bishops. Often the official reaction depended on the views they were endorsing, thus priests in Italy working for abortion or divorce laws have been suspended while others in Spain or Latin America working against a repressive government have been tolerated.

Since his election in October 1978, John Paul had made it clear that he favors social reform but does not believe that in most cases priests should be leading or organizing it.

In other words, the pope's idea of activism is one that focuses on moral issues and rejects or avoids partisan entanglements.

One Jesuit here suggested that the pontiff's objection to Drinan's career reflected the pope's judgment that it was not a situation involving "concrete and exceptional circumstances. I guess he thought there were plenty of laymen to play Father Drinan's role," the Jesuit said.

The pope first made his restrictive view of priests' roles clear at Puebla, Mexico, in January 1979 when he told the members of religious orders "you are not social directors, political leaders or functionaries of a temporal power."

At that time he asked priests to remember that "temporal leadership can easily become a source of division, while the priest should be a sign and factor of unity and brotherhood."