(Exodus 22:10) states: "The oath of the Lord shall be between the two of them." The Mekhilta extracts four separate legal principles from this single phrase, each based on the words "between the two of them."
First: "between the two of them" — to exclude the heirs. If one of the parties dies, the oath mechanism does not transfer to his inheritors. The oath is personal to the two original disputants.
Second: "between the two of them" — to include an oath in cases where one party is suspect. If one litigant is not trusted to swear honestly (because of a history of dishonesty), the oath shifts to the other party. The trustworthy party swears and collects.
Third: "between the two of them" — to exclude the judge. A judge cannot force a party to swear against his will. The oath must be taken voluntarily by the party to whom it applies. Judicial coercion in oath-taking is forbidden.
Rabbi Nathan added a fourth reading: "between the two of them" means the oath devolves upon both parties equally. Both litigants bear responsibility for the oath's sanctity. If a false oath is sworn, the spiritual consequences fall not only on the one who swore but on both participants in the judicial process.
Four words — "between the two of them" — yielded four independent legal principles. The Mekhilta demonstrates that Torah language operates at a density that far exceeds ordinary speech.