The Supreme Court, expanding the constitutional guarantee of religious freedom, ruled yesterday that states may not deny unemployment compensation to people quitting jobs for religious reasons.

The ruling underscored the court's previous holdings that even indirect incursions on fundamental liberties cannot be justified by the government's need to save money.

The justices also warned states and lower courts to stay out of the business of interpreting the correctness of someone's religious conviction, whether or not it conforms to the doctrines of the person's faith. "Courts are not arbiters of scriptural interpretations," the justices said in an 8-to-1 ruling.

The case concerned a Jehovah's Witness who quit his job at an Indiana factory making turrets for military tanks, citing his faith's traditional prohibition on participating in war and war-related activity. Eddie Thomas had been transferred into the turret manufacturing department of the Blaw-Knox Foundry and Machinery Co. after the closing of the department where he worked previously.

Indiana, like all states, generally denies unemployment compensation to those voluntarily leaving a job, and it made no exception for Thomas. Thomas argued, however, that the denial represented a state intrusion into his First Amendment right to the free exercise of religion.

The case confronted the justices with delicate religious questions, similar to those it has faced in dealing with conscientious objectors, flag salutes and compulsory education.

The Indiana Supreme Court rejected Thomas' argument. The court did not question Thomas' sincerity, but, nothing that another Jehovah's Witness had continued to work at the same factory, it said Thomas was unclear in his views of what his religion required and that his decision was a "personal philosophical choice rather than a religious choice."

Chief Justice Warren E. Burger, writing for the majority, yesterday reversed the Indiana court, basing his ruling on a 1963 Supreme Court decision in favor of a Seventh-Day Adventist denied unemployment benefits after being fired for refusing to work on Saturday, the Adventist Sabbath.

States may not condition important benefits upon conformity to conduct prohibited by a religious faith. Burger said yesterday. That puts "substantial pressure on an adherent to modify his behavior and to violate his benefits."

Such an intrusion is justified only when a state has a compelling interest in doing so and uses the "least restrictive" means to advance that interest. Indiana's claim that paying Thomas would produce a flood of unemployment claims from people quitting jobs for "personal" reasons meets neither criterion, Burger wrote.

Burger also criticized the Indiana court for questioning Thomas' interpretation of his faith. "The determination of what is a 'religious' belief or practice is more often than not a difficult and delicate task," Burger wrote. But "the resolution of that question is not to turn upon a judicial perception of the particular belief or practice in question; religious beliefs need not be acceptable, logical, consistent or comprehensible to others in order to merit First Amendment protection."

Justice William H. Rehnquist dissented from yesterday's ruling, saying it "adds mud to the already muddied waters" of church-state legal questions and fails to offer "meaningful guidance to other courts. . . . "

In other action yesterday:

The court ruled unanimously the federal law guaranteeing the "prevailing wage" for employes of federal contractors does not give workers the right to sue to collect those wages.

The case, Universities Research Association vs. Coutu, stemmed from work performed under a contract with the old Atomic Energy Commission for construction on the Fermi National Accelerator Laboratory. The AEC (since folded into other government energy agencies) determined that the Davis-Bacon Act, which guarantees the prevailing wage in a locality, did not apply to the work.

Stanley E. Coutu, a mechanic on the project, sued in April 1975 to recover back wages for himself and others. But the court ruled yesterday that Congress had not authorized individual suits under the act.

Such questions about the individual right to sue, as opposed to government's ability to sue, are expected to become increasingly important if the Reagan administration follows through on promises to reduce the federal government's role in filing suits.

The court ruled, 7 to 2, that truck drivers can sue for wage claims even if the claims have been submitted to voluntary arbitration through labor relations mechanisms. The case, Barrentine vs. Arkansas-Best FREIGHT System Inc., involved interpretation of the Fair Labor Standards Act and a dispute over payment for time spent by drivers conducting required safety inspections of their trucks.