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 for Rabbi Zeira, explained in Bava Metzia] would recover, he would make a day of festivity for the rabbis. [Rabbi Zeira] recuperated and [Rabbi Avahu] made a festive meal. When it was time to begin the meal, [Rabbi Avahu] asked Rabbi Zeira to be botzeia (break bread). He responded: Don’t you agree with Rabbi Yochanan, who said that the host is botzeia? So [Rabbi Avahu] was botzeia. When it was time for Birkat Hamazon, [Rabbi Avahu] asked [Rabbi Zeira] to lead. He responded: Don’t you agree with Rabbi Huna of Bavel, who said that the botzeia leads Birkat Hamazon? [Rabbi Avahu], for his part, held like Rabbi Yochanan that the host is botzeia, but the guest leads Birkat Hamazon. Ein Ayah:
Although a life of asceticism, even if embarked upon for noble reasons, is not the desired path for the masses, there will always be some people with high spiritual goals and discipline who feel it is right for them, specifically. Rabbi Zeira was such a person, and, therefore, he disagreed with the message Rabbi Avahu was trying to send by making a festive meal, i.e., that no one should see extreme self-deprivation as a goal. Rabbi Zeira believed that asceticism could still be important for individuals, as the desired paths of religious life can be broad and disparate, according to the individual’s level and characteristics.
Rabbi Zeira did not totally disagree with Rabbi Avahu’s message, as he agreed that asceticism is not the path of choice for the masses, and he also did not want to show disrespect to Rabbi Avahu by boycotting his feast. On the other hand, Rabbi Zeira did not want to give the impression that he had retracted his approach and now wished the world be without asceticism. Therefore, Rabbi Zeira did not want to take an active role in the meal, by either being botzeia or by leading Birkat Hamazon but saw himself as a mere guest, even though it was in his honor.
There is a philosophical disagreement with some practical ramifications between great thinkers as to the proper outlook on the place of physical enjoyment. One approach finds independent value for physical pleasures and benefits, beyond their being needed to enable spiritual gain. The other approach sees it as a burden and liability for those who have a bright and sensitive spiritual/intellectual side. Rather, it should only be seen as a tool to enable the body to lead the person on a path of straightness and pursuit of wisdom, which is a foundation of his completeness. One who takes the second approach would want to connect breaking bread to Birkat Hamazon, as the latter focuses not on the experience of eating but on its practical benefits. By having the same person do both (as Rabbi Zeira proposed, one shows that the value is not in breaking bread alone, but only in what it facilitates.
In contrast, Rabbi Avahu felt that if one approaches the enjoyments of the world in a balanced, thought-out manner, it can be a good thing in and of itself. In fact, it is a means of accepting Hashem’s kindness and goodness that He desires to bestow upon His creations. This follows the approach that one should partake of every species Hashem created (Yerushalmi, Kiddushin 4:12), as one must take advantage of all permitted enjoyment Hashem prepared for us. According to Rabbi Avahu, it is an honor to be botzeia even if he will not also lead Birkat Hamazon, and the host can be botzeia while the guest leads Birkat Hamazon.