One of the passages most familiar to Jews who regularly pray and study Torah is that which is said at the conclusion of the Uva Letzion prayer:

"G-d wished for the sake of His righteousness to magnify Torah and glorify it." (Yeshayahu 42:21)

There are many dimensions to this concept of magnifying the Torah. In our gemara it is applied to explaining why the Torah went to such lengths to teach us that the presence of scales on a fish is the definitive proof of its kosher status. Even though it could simply have written the word kaskesses and relied on a passage elsewhere to define that word as "scales", the Torah underscores this by including the word "fins" in the identifying signs of kashrut. This seems superfluous since any fish which has scales also has fins. It is there only to ensure that we will not mistakenly translate kaskesses as fins and rely on that feature alone as a sign of kashrut. This seemingly superfluous proof is there in order to magnify and glorify the Torah we study.

Rabbi Chananya ben Akashya (Mesechta Malkot 23b) expands on this perspective. Because G-d wished to endow Israel with greater opportunity for merit, he points out on the basis of the passage, He gave them much Torah and many mitzvot.

While these gemaras focus on the role of G-d in magnifying the scope of His Torah, a somewhat different interpretation is offered by Metsudat David in his commentary on Yeshayahu. After the prophet has castigated those with Torah knowledge and commitment for being blind and deaf to the faults of their generation, and failing to reach out to their fellow Jews, he reminds them that the reason they were blessed with knowledge was because G-d wished them to bring righteousness to others and to magnify and glorify the Torah by teaching it to them.

We sometimes find that we are capable of understanding a Torah passage only by relying on a signal from another one.

A case in point is the passage which describes the need for an atonement by sacrifice if "one touches a carcass of an unclean beast or a carcass of unclean cattle" and subsequently forgets about it only to later "become aware and be guilty." (Vayikra 5:2) There is no indication in this passage as to what guilt requiring atonement there is in merely becoming ritually unclean through contact with a carcass.

The Sage Rebbie (Rabbi Yehuda Hanassi) solves this mystery by deducing a superfluous term in this passage. Another Torah source has already taught us that wherever the term "beast" is used it includes cattle as well and vice versa. If the passage has already mentioned the result of touching the carcass of a beast there is no need for mentioning the carcass of cattle. His conclusion therefore is that the inclusion of the cattle carcass is a signal to connect this passage with another in which the same term appears.

That other passage is in Vayikra 7:21 and it informs us that one who touches the carcass of dead cattle and, in his impure state, knowingly eats the sacred flesh of a sacrifice is punished by extirpation. Just as the guilt for which one is deserving such harsh retribution is the result of consciously consuming sacred flesh so too is the atonement required for one who committed this same offense out of forgetfulness related to the eating of sacrificial flesh.

This methodology employed by Rebbie in reaching this conclusion is that of gezeira shave a similarity of terms in two different places which allows for making an equation. But it was possible to apply this method only after detecting the signal to do so communicated by that superfluous term.

• Chullin 71a