The Fairfax County Board of Supervisors this week opened another major part of Reston to development, but rejected a request by the county Housing Authority to set aside 15 percent of the land for subsidized housing.

The rezoning plan approved by the supervisors covers 362 acres in northern Reston, and opens the way for the Reston Land Corp., a subsidiary of Mobil Oil Co., to build apartments, town houses and single-family homes for about 3,500 people. Reston, a planned community created in 1965 to have a population of 78,000, currently houses about 37,000.

The Fairfax County Redevelopment and Housing Authority urged the supervisors to use the rezoning request as a lever to guarantee a sizable number of homes for low- and moderate-income families. The authority wanted to develop 15 percent of the land itself, with the county rewarding Reston by permitting it to increase the housing density in other parts of the town.

But the Housing Authority, which lately has had more than its usual share of political troubles, was rebuffed. The Reston Land Corporation wanted no part of the binding requirements, and neither did the supervisors, marking the second time in recent weeks that Housing Authority plans for subsidized housing have been rejected.

"It sounds like another midnight raid by the Housing Authority," said board Chairman John F. Herrity, a Republican who has been one of the most vocal and persistent critics of the authority.

Angered by what some supervisors considered last-minute maneuvering tactics by the authority, the board did not need any persuading to ignore the authority's request and a less far-reaching proposal suggested by the county planning commission. The supervisors got some persuasive oratory anyway from veteran zoning attorney E. A. Prichard, who cited sources as diverse as Reston's 19-year-old housing policy and the New Testament to bolster the Reston Land Corp. case against requiring subsidized housing.

About 13 percent of the existing homes in Reston were built or are rented with some form of government subsidy for low- or moderate-income families, Prichard said, and county housing officials confirm. Arguing that Reston consistently has offered a variety of housing types and prices, Prichard said the county should not impose new restrictions.

"We've got more subsidized housing than any other part of the county," Prichard said. "We'd hate to have to swear that we're honest."

To bolster his case, Prichard cited the Epistle of St. James 5:12: "But above all, my brethren," the verse reads, "do not swear either by heaven or by earth or with any other oath, but let your yes be yes and your no be no, that you may not fall under any condemnation."

"We didn't wish to fall under condemnation," Prichard said.

The Housing Authority has been trying, with only moderate success, to reserve homes in the increasingly expensive Fairfax County housing market for poor and middle-income families. Statistics released last week by the county showed that only 45,613 of Fairfax's 220,086 housing units were valued at less than $80,000 in January, down from 63,935 such homes only one year before. In January, the median price for a single-family home in Fairfax was $97,000, according to county officials.

Attempts to build public housing in the county's more affluent neighborhoods, however, have consistently encountered strong opposition. Last month U.S. Rep. Stan Parris (R-Va.) responded to such opposition and persuaded federal housing officials to effectively kill a proposed project in Springfield in southeastern Fairfax, where a private developer would have built 30 single-family homes as public housing. Parris also asked the U.S. General Accounting Office to look into the authority's use of funds.

Supervisor Nancy K. Falck, a Republican whose Dranesville District is just north of Reston, said her area doesn't need more subsidized housing either. "I don't believe it would be to the benefit of the community and the people who would be served there to add an additional impact," she said.

Both Falck and Supervisor Martha V. Pennino, a Democrat who represents Reston, said they resented the Housing Authority's last-minute attempt to place the restrictions on the Reston rezoning. "It seems to me the Housing Authority had no sensitivity to the fact that all of this had been very, very carefully worked out," Falck said.

However, Supervisor James M. Scott (D-Providence), one of the authority's few consistent supporters on the board, pointed out that the authority had first suggested the plan for subsidized housing last February. He said the proposal was not communicated properly to Pennino and Falck, and he asked the county staff to find out why.