Supreme Court Justice Byron R. White yesterday blocked temporarily the jailing of New York Times reporter M. A. Farber for refusing to surrender his notes and files on a murder case to a New Jersey judge.

White acted less than an hour before Farber was to begin serving an open-ended jail term for civil contempt of court.

He stayed the jailing order and other penalties pending a response from attorneys for Dr. Mario Jascalevich, the defendant in the murder trial, to Farber's and The Times' request for a stay until issues in the contempt case are resolved. White gave them until noon Tuesday to respond.

Lawyers for Farber and The Times sought the stay in a 30-page petition, backed up by two inches of supporting documents. They asserted that the "very existence of a vital, unfettered press rests on its being free from the type of punishments" faced by Farber and The Times.

They asked that the contempt order be stayed until the full Supreme Court can consider the case or until the New Jersey courts resolve the free-press issues raised by The Times and Farber in their fight against being forced to surrender Farber's notes and files.

The Supreme Court is in recess until October.

Earlier this week the Superior Court in Bergen County, N.J., ordered Farber to remain in jail and The Times to pay a fine of $5,000 a day until Farber surrenders his confidential materials on the Jascalevich case.

Farber and The Times were also convicted of criminal contempt, for which Farber was sentenced to six months in jail, to be served after he surrenders the files, and The Times was fined $100,000. These penalties have been stayed pending a hearing.

Farber's notes were subpoenaed by Jascalevich, who is on trial in Hackensack, N.J., on charges of killing five hospital patients with lethal doses of curare, a powerful muscle-relaxing drug. It was articles by Farber on mysterious deaths during 1965 and 1966 at an Oradell, N.J., hospital where Jascalevich worked that led prosecutors to renew an investigation of the deaths. The investigation resulted in indictment of the doctor.

Jascalevich's lawyers contend that Farber's investigative files are vital to their client's defense, while Farber and The Times argue that the confidentiality of news sources is vital to a free press and is protected by the Constitution as well as by news-gathering shield laws in some states such as New Jersey.

"To this day, petitioners (Farber and The Times) have not been afforded a hearing by any court on their claims under the First and Fourteenth Amendments or on their claims of statutory protection of newspersons' rights under various state shield laws," the petition to the Supreme Court said.

"We submit that the very existence of a vital, unfettered press rests on its being free from the type of punishments visited upon petitioners prior to a judicial determination of their rights," it added.

Without assurances of anonymity for news sources, said attorneys for Farber and The Times, reporters will be "relegated to the reporting of news stories which are less probing, less factual and hence less informtive." The damage is "hard to quantify" but is "nonetheless real and immediate," they added.

Farber spent almost seven hours in jail last Monday before a state Supreme Court justice granted a stay of the civil penalties pending a hearing before the full state Supreme Court. The court later refused to grant Farber a further stay but agreed to give him until noon yesterday to seek a stay from a U.S. Supreme Court justice.

The request for the stay was submitted to Justice William Brennan Jr. but was acted upon by Justice White in Brennan's absence.

It was The Times' second trip to the Supreme Court in the case. Earlier, before the contempt penalties were levied, both White and Justice Thurgood Marshall refused to issue a stay but did not rule out such action later in the proceedings.