(condensed from Ein Ayah, Berachot 7:5)

Gemara: Rabbi Zeira became weak, and Rabbi Avahu went to visit him. Rabbi Avahu accepted upon himself that if “the small one with burnt thighs” [a nickname explained in Bava Metzia] would recover, he would make a day of festivity for the rabbis.

Ein Ayah: Rabbi Zeira chose a path of extreme humility, treating himself as one who is far from proper shleimut in service of Hashem and pure characteristics. That is why he accepted upon himself a life of asceticism, as described in Bava Metzia 85a. This is hinted at in his nickname of “burnt thighs,” for the body can be compared to a leg in comparison to the godly soul. The idea behind the burnt thighs is that if one deprives his body of what it needs, the spirit will also lack the status it deserves. Rabbi Zeira needed to know that he did not need any more self-affliction, such as multiple fasts, which weakened his body. The reason they called him small is that he saw himself as lacking due to his extreme humility, as Chazal said about the biblical Yoktan (Bereishit Rabba 6:4). Although the humility is basically good, cases of excess, such as the story in which his legs were burnt, were unfortunate.

Rabbi Avahu suspected that Rabbi Zeira’s illness might have to do with his traditional self-deprivation. To stress that this is not proper for those who learn Torah (see Ta’anit 11b), he pledged specifically to make festivities for the rabbis if Rabbi Avahu recovered to show that some indulging is good, as the rabbis should avoid deprivation. It stresses that he made the meal for all of the rabbis to show that the path of healthy living is a mainstream one for them. Extreme behavior is appropriate only for extreme cases or people.