In the third chapter of Pirkei Avot, which G-d-willing we will learn on Shabbat, Chazal emphasize the message we learned in the second chapter that there is no Torah without derech eretz (3:17). The Maharal in his commentary, Derech Chaim, explains that derech eretz in this context refers to the normal considerations that must be addressed by people to get by in the world. This means that before somebody can become a Torah scholar, he has to make sure he can earn a living and take care of his other responsibilities.
We have been given the Torah not to remove us from practical considerations or to become detached from practical concerns, but as an enhancement of our experience of reality, building upon the foundation that we establish for it. The entire world was created for the Torah, so without Torah there would be no need for material existence at all, but if we do not attend to our material needs then we cannot possibly learn Torah, let alone appreciate its value.
The Mishna goes on to say (ibid.) that without flour, there is no Torah, and without Torah, there is no flour. Rav Chaim Volozhin in Ruach Chaim teaches that although it is true that man cannot live on bread alone, one cannot possibly learn Torah if he hasn’t first secured his material necessities. The Maharal notes that the Torah itself is not infrequently identified as “bread,” so it’s noteworthy in this context that the Mishna specifies flour rather than bread. But the meaning of this allegory is that the Torah sustains the soul as bread does the body, and if the body isn’t first sustained, then it isn’t possible to graduate to the spiritual level of Torah.
Flour is the most basic ingredient needed to feed the body, but once it is made into bread, it becomes more associated with physical urges and pleasures and thus potentially detrimental to spiritual growth. Therefore, says the Maharal, the Mishna specifies flour to place the emphasis on providing for material needs rather than on satisfying physical urges.
Furthermore, if the Mishna had said there must be bread to learn Torah, we might understand that to mean simply that somebody has to have eaten on the day he wishes to learn Torah. However, the specific reference to flour – which must be processed into bread – also denotes long-term planning. A person doesn’t merely have flour because he’s hungry at the moment, but he must collect and store flour so that it’s present in sufficient quantities when the time comes to make the bread. This means that in order to properly learn Torah, it is necessary not only to feed the body in the moment, but to devote oneself to addressing practical considerations in feeding oneself and one’s dependents.
The Maharal also notes that following other similar formulations in this Mishna and elsewhere, we’d expect the most important aspect of the pairing to be listed first, i.e., Torah should come before flour. He suggests that one possible explanation for this is because the concern for one’s sustenance is so critical to learning Torah that in essence the necessity of earning a living is on a par with Torah study because effectively accomplishing the former is the only way that proper Torah study becomes possible.