Eruvin 72 - 78
“The strength of permitting is better.”
This rule is taught on our daf to explain why a Tana chose to teach in one manner rather than another. Our gemara states that he chose the manner that emphasized the opinion of the lenient opinion, since that is “better”.
Why is this so? Rashi elsewhere (Beitza 2b) explains that one who permits and is lenient has learned this with certainty from his teachers, and therefore has no qualms about ruling leniently. To rule strictly, however, does not require reliance upon what he heard from his teachers, and he may be strict even when something is permitted.
- Eruvin 72b
“This”, and there is no need to say “that”,is how he taught it.
This somewhat enigmatic statement is how the gemara explains why two cases are taught in a beraita on our daf even though teaching one case would suffice to know the ruling in the second case as well. (The topic in the beraita is if the height of a window in a wall between two courtyards affects the halachot of of eruvei chatzerot there.)
If one case would be enough, why indeed is the second case taught? One explanation of the Shelah Hakadosh (Rabbi Yeshaya HaLevi Horowitz, 16th century, Prague) is that the Tana heard both cases, taught at separate times, each one from a different Tana. In order to preserve the integrity of the Torah teachings he had learned, he taught them both.
- Eruvin 76a