Rabbi Yossi Haglili confronted a problem in the Torah's legislation about seduction. The verse states that when a man seduces an unmarried woman, "money shall he pay" (Exodus 22:16). But the Torah does not specify how much. The amount is left unstated — an unusual gap in a legal code that is otherwise precise about penalties.
Rabbi Yossi was not content to leave the question open. He employed a classic rabbinic technique: gezerah shavah, linking two passages that share a keyword. The verse about seduction says "money." Elsewhere, in (Deuteronomy 22:29), the Torah prescribes the penalty for a man who ravishes a woman: "he shall give the father of the girl fifty silver." That verse also uses the word "money."
The shared keyword creates a bridge between the two laws. Rabbi Yossi reasons: just as in the case of ravishment the Torah specifies fifty pieces of silver, so too in the case of seduction, the unspecified "money" must mean fifty. The parallel language demands a parallel amount.
This passage from the Mekhilta DeRabbi Yishmael illustrates how the rabbis read the Torah as an interlocking legal system, where no word is wasted and every repetition carries meaning. A single word — "money" — appearing in two different contexts allows the sages to fill in what the Torah left implicit. The technique assumes that the Torah speaks with perfect consistency, and that the reader's task is to discover the connections hidden beneath the surface of the text.