THE BEECH-NUT people can't say they didn't know the rules. They're right there in Leviticus 19:35-6. "Ye shall do no unrighteousness in judgment, in meteyard, in weight, or in measure," the Almighty instructs. "Just balances, just weights, a just ephah, and a just hin, shall ye have."

Beech-Nut's problem was with the just hin, which turns out to be a liquid measure. The nation's second-largest baby food manufacturer, a subsidiary of Nestle S. A. of Switzerland, was indicted a year ago for selling adulterated apple juice. The indictment said it had knowingly sold millions of jars of the phony stuff in 20 states, Puerto Rico, the Virgin Islands and five foreign countries over a period of years. It seemed hard to believe; after all, this is baby food we're talking about. Any violations were "technical," the company said stiffly at the time.

But now it has pleaded guilty. What it sold as 100 percent apple juice was actually not very much apple juice at all; it was a sweet liquid made from such ingredients as beet sugar, cane sugar syrup and corn syrup. Its virtue from the standpoint of the company was that it was 20 percent cheaper than the real thing.

The company has agreed to pay a $2 million fine. That is said to be a record for a violation of this kind, and Assistant Attorney General Richard Willard hoped that it would "send a strong message that consumer fraud will not be tolerated by the government." Another prosecutor called the company's decision to admit its guilt rather than contest the charges "refreshing."

We suppose all this is true, and there is no indication any baby was harmed by the phony juice. But a $2 million fine, vast as it may be in the history of the food and drug act, is only a footnote in an annual report. The Old Testament contains a different standard: "And if ye will not yet for all this hearken unto me . . . I will break the pride of your power; and I will make your heaven as iron, and your earth as brass." The next time a mighty corporation cheats on baby food, maybe that's the way to go.