Rebbi — Rabbi Yehudah HaNasi — analyzed the phrase "until elohim shall come the matter of both" (Exodus 22:8), which describes disputes brought before judges. The verse speaks of "both" parties, indicating that two litigants are involved. But how many judges must hear their case?
Rebbi noticed a subtle grammatical clue. The Hebrew verb "yarshian" — "shall incriminate" — is written without a vav, which indicates a singular subject. If it were written "yarshiyen" with a vav, it would indicate two subjects. Since only one judge is grammatically implied, but two litigants are already established, the total so far is three people involved in the proceeding — two parties and one judge.
But there is a further principle: "there is no equally balanced beth din." A court with an even number of judges could deadlock. Therefore, an additional judge must be added to ensure an odd number. Starting from two parties and one judge, adding a second judge creates an even number, so a third is needed.
From this analysis, Rebbi derived the foundational ruling: monetary cases are judged by three judges. This became one of the bedrock principles of Jewish judicial procedure. A single verse about two quarreling parties, parsed with attention to a missing vowel letter, produced the standard court composition that governed Jewish civil law for millennia.