The passage we're looking at starts with the phrase, "And a man lie with her a lying of seed." Now, at first glance, this might seem straightforward. But the rabbis of the Sifrei Bamidbar, an early rabbinic commentary on the book of Numbers, saw much more beneath the surface. They didn’t just read the words; they interrogated them!
The first thing they pointed out is the seemingly redundant phrase "a man." Why not just say "he"? Well, the rabbis interpreted "a man" to specifically exclude a minor. The text is talking about an adult male, someone responsible for their actions.
But the real interpretative fireworks start with the phrase "lie with her." The rabbis ask, "Why 'her'? Why not just say 'lie with'?" It's in this "her" that they find a prohibition against something not explicitly stated: incest. this way: they use a type of logical argument called qal va-chomer (קל וחומר), or "light and heavy." It's a way of reasoning from a minor case to a major one, or vice versa. The Sifrei Bamidbar sets up this argument: If a husband, who only forbids his wife to other men temporarily (since he could divorce her), finds himself forbidden to her if she commits adultery (she "forbids her forbidder"), then how much more so should a man be forbidden from sleeping with his sister-in-law, whom he is forbidden to be with always?
It’s a clever argument. The Torah doesn't explicitly say, "You shall not lie with your sister-in-law." But the rabbis use the phrase "with her" to infer that the text implies it. The Torah specifies "her," meaning not another woman he is forbidden from being with.
Abba Channan, quoting Rabbi Eliezer, takes this interpretation even further. He argues that "with her" excludes not only the sister-in-law, but also the mother-in-law and any of the other illicit relations forbidden by Torah law. Again, they use the qal va-chomer argument: If a relatively "light" act of forbidding (like a husband forbidding his wife, but only temporarily) can result in the wife forbidding the husband if she cheats, then how much more so should a "grave" act of forbidding (like incest, which is forbidden permanently) result in the man being forbidden from the act?
It's a powerful example of how the rabbis saw the Torah not as a static text, but as a living document, pregnant with meaning. They believed that every word, every phrase, even the seemingly insignificant ones, held the key to unlocking deeper truths about morality, law, and the relationship between humanity and the Divine. This approach, meticulously dissecting the text and drawing logical inferences, highlights the profound depth of rabbinic interpretation. It shows us how, through careful reading, the rabbis expanded upon the basic laws of the Torah to address a wider range of ethical and legal situations, ensuring the continued relevance of the sacred text for generations to come.