The world is divided into two realms: ruchniyus and gashmiyus, otherwise known as Heaven and earth. The distance separating Heaven and earth is tremendous. They seem so far apart and so different from one another. But there is a middah that unites them.
This middah, called yesod, causes Heaven to become Heaven and earth combined. And similarly, earth becomes earth and Heaven combined. In other words, gashmiyus becomes gashmiyus and ruchniyus together, and so too with ruchniyus. For example, when a Jew eats on Shabbos, it’s not just a physical act. On Shabbos, the gashmiyus is ruchniyus, and the ruchniyus is gashmiyus. Furthermore, ruchniyus penetrates Friday, and thereby penetrates the other weekdays as well. Although Friday is mundane and Shabbos is sacred, the Torah gave us the opportunity to unify the weekdays with Shabbos through the middah of yesod, which unifies gashmiyus and ruchniyus for the entire week.
This middah of yesod, of unifying Heaven and earth, is the special middah of Yosef HaTzaddik. This is the innovation in avodas Hashem that Yosef brought into the world: the ability to unify gashmiyus and ruchniyus. This is what he accomplished by successfully withstanding his great nisayon. He showed that through gashmiyus, a person can become a holy tzaddik. This is in fact what happens when a person overcomes the influence of gashmiyus, as Yosef did — the gashmiyus turns into ruchniyus for him. Through passing his nisayon, Yosef merited rulership and sanctity, for he unified Heaven and earth.
Friday is what integrates these two worlds. And here lies the difference between a Jew and a non-Jew. For a non-Jew, there is a tremendous gap between ruchniyus and gashmiyus. They are cut off from one another. When he eats, he is totally physical, and when involved in matters of the spirit, he is totally otherworldly and saintly.
The middah of yesod expresses a Jew's true character. When a Jew eats, he is spiritual. And when he learns Torah, he connects to the Torah so profoundly that it is not just a spiritual matter for him; he actually enjoys it.
This idea is expressed by a verse written about b'nei Yisrael's leaders at Mount Sinai: "They gazed upon God, and they ate and drank." (Shemos 24:11) Targum Onkelos explains that they were so happy over their korbanos, which Hashem had graciously accepted, that they felt as if they had eaten and drunk. For them, sitting in the beis midrash was like sitting at a banquet.
For a Jew, Heaven and earth are not cut off from one another. Learning Torah is geshmak: It's tasty and enjoyable! Among the foundations of Yiddishkeit are two important factors: A person should truly enjoy his learning and that even when he is involved in gashmiyus he shouldn't disconnect from ruchniyus.
Friday is preparation for Shabbos. On the one hand it is a mundane day, and on the other hand it is completely sacred. It is a special day of kedushah that unifies Heaven and earth. Thus, it is especially important to learn Torah on Friday and not let this precious day slip through our fingers. It is a great loss for us to treat the crucial time of Friday as if it were a “day off” from avodas Hashem. By properly appreciating and utilizing Friday, with its unique middah, we can unify Heaven and earth!
