The Torah addresses the case of a master who strikes his slave in (Exodus 21:21), using a phrase that puzzled the rabbis: "But if one day or two days." On the surface, this seems to distinguish between a slave who survives one day after being struck and one who survives two days. But the Mekhilta finds something far more precise hidden in this language.
If taken literally, the verse would mean that a different rule applies depending on whether the slave survives exactly one day or exactly two days. But Scripture also says "if one day," which appears to collapse the distinction. So how can both readings be true at the same time?
The Mekhilta resolves the contradiction with an elegant principle: "one day which is like two days; two days which are like one day." The answer is a single twenty-four-hour period. Whether you count it as one day or as spanning two calendar days, the legal threshold is the same — twenty-four hours from the moment of the blow.
This interpretation demonstrates the rabbinic method at its sharpest. An apparent contradiction in Scripture is not a flaw to be explained away. It is a signal, an invitation to look deeper. The tension between "one day" and "two days" is deliberate, placed there by the Torah to teach a specific legal measurement that neither phrase alone could convey.
The result is a precise standard of justice: if the slave survives beyond twenty-four hours, the master is treated differently under the law. The Torah's seemingly contradictory language is actually its most efficient way of communicating an exact legal timeframe.