Pirkei Avot Chapter 2 Mishnah 2: Rabban Gamliel the son of Rabbi Judah HaNassi would say: Beautiful is the study of Torah with the way of the land (derech eretz), for the toil of them both causes sin to be forgotten.
The simple meaning of this teaching is that our main mission is to study Torah, but as we cannot learn Torah exclusively and must make a living, we should add earning a livelihood – called derech eretz (literally, ‘the way of the land’) to our schedule. When a person toils at both Torah study and earning a living, he doesn’t have much spare time to engage in sin.
There is, however, a different explanation according to which derech eretz is greater than Torah. This is the explanation for the teaching of the sages, “Derech eretz preceded the Torah”, which posits that the precedence of derech eretz is not only in time, but in stature, as well. The third Lubavitcher Rebbe, the Tzemach Tzedek, brings four explanations for this concept:
The first explanation: The proper way (derech) of service of God must be accompanied by identification with the lowliness of the earth (eretz). The main rectification of a person is his recognition of his essential lowliness – how distant he is from God. Before we begin to study Torah we must contemplate on this and identify with our very lowly, weak human nature. This is reflected at the end of the Silent Prayer, in which we first say, “And may my soul be as dust to all,” and only then do we merit to ask for the next stage, “Open my heart to Your Torah.”
The second explanation: The word eretz is cognate to the word ratzon, ‘will’ and ratz, ‘running’. The eretz, land, wills to run to God. “Why was it called eretz? Because it wanted (ratzta) to do the will (ratzon) of its maker.” The numerical value of derech eretz is the same as tefillah, prayer. This teaches us that the main time that we have a will to run to God is when we are praying to Him. Prayer is the ascent from the lowly land to God. According to this, “Derech eretz precedes Torah” is prefacing our Torah study with prayer, as in the Mishnah: Rabbi Nechunyah ben Hakaneh would pray a short prayer when he entered the study hall and when he exited.”
The third explanation: Derech eretz refers to Jewish customs, which take precedence in their stature over the laws of the Torah: “The words of the scribes (the directives of the sages) are dearer than the words of Torah (the directives of the Torah).” The expression derech eretz is explained here as the ‘way of the world.’ The customs that were accepted by the Nation of Israel, as per the directives of the sages, are higher in stature than the directives of the Torah.
The fourth explanation: Derech eretz refers to Jewish unity. In Kabbalistic terms, the Torah is “the World of Rectification,” but above that is the “World of Binding” (Olam Ha’akudim) in which all the souls are bound together in one vessel. When unity reigns – even unity among criminals – its root is in the lofty World of Binding. This is the derech eretz that is higher in stature than the World of Rectification – the Torah.
 See Rashi, Rabbeinu Yonah and more.
 Vayikrah Rabbah 9:3.
 Ohr Hatorah, part 3,p.583.
 From Elokai Netzor at the end of the Silent Prayer, see Ta’anit 17B.
 Breishit Rabbah 5:8.
 Berachot 28B.
 As per the Jerusalem Talmud, Brachot 1:4; Avodah Zarah 35A.
 Siddur with D”ach starting from ושאבתם מים.