There were horses in the receiving line, four of them - fortunately under the steady rein of the U.S. Park Police - at the red-carpeted entrance to Garfinckel's on Friday night.

The occasion was a cocktail and dinner benefit for the Washington International Horse Show, which opened last night, and the show sponsor, "People-to-People," a nonprofit organization founded in 1956 to promote international friendship by funding sports exchange programs between the United States and other countries.

The Washington International which runs through next Sunday at the Capital Centre, is according to former president Bruce Sundlun, the biggest indoor show on the North American continent with "more horses, more days and more attendees" than Madison Square Garden or Toronto.

Among those at Friday's benefit were the ambassadors of Belgium, Canada and Ireland, whose countries' teams will be competing with the United States in the international jumping.

Garlinckel's store personnel were in riding attire and even one long-skirted habit. (Said one, "It took me three hours of practice to learn to tie my stock.") When asked if Garfinckel's was now in the riding apparel business the reply was, "No, we rented these for the evening," and then, "God, it cost me $4,000 to outfit four boys - I've got to get these back first thing tomorrow morning."