Following the lead of the Chasam Sofer, I believe that we can explain why the “vav” of "גחון" was chosen as the midpoint of the letters of the Torah when the Torah was yet contiguous permutations of holy names—i.e. before the legs of the nachash were excised, before it was compelled to travel on its belly. Additionally, what does this fact come to teach us nowadays, after the legs of the nachash were excised?
We can suggest that it alludes to Shevet Zevulun, the sixth of the twelve shevatim fathered by Yaakov Avinu, in this order: Reuven, Shimon, Levi, Yehudah, Yissachar, Zevulun. Now, Rashi teaches us a fundamental principle regarding the letter “vav” (Bereishis 17, 9): The letter “vav” adds on to the previous subject. The letter “vav” (whose gematria is six) connects an item to the item preceding it. With this in mind, we can suggest that HKB”H arranged for Zevulun, Yaakov’s sixth son, to be born immediately after Yissachar, Yaakov’s fifth son, the pillar of Torah. In other words, Zevulun was the connecting “vav.” This was designed to illustrate the intimate relationship between Zevulun and Yissachar. Zevulun’s role was to provide for and support Yissachar’s life of Torah.
Furthermore, Rashi explains: "כל הולך על גחון"—whatever crawls on its belly: This refers to a snake. The term »גחון« means bending low; for, it moves bent low and falling on its belly. Thus, HKB”H established the enlarged “vav” of the word »גחון« to be the midpoint of the letters of the Torah as a reference to the nachash. In this manner, we are being taught that the original purpose and plan was for the nachash and man to be connected—alluded to by the connecting “vav”—such that it would enable man to devote himself to the study of Torah and service of Hashem. It was meant to use its legs to run around and take care of all of man’s mundane needs. Had it fulfilled this original purpose, we would not have the combination of words of "כל הולך על גחון"; instead, we would have permutations of holy names that would help the nachash fulfill its intended role.
However, this was not to be. The “nachash hakadmoni,” in cahoots with the “samech-mem,” mutinied. Instead of assisting man to study Torah and serve Hashem, it persuaded Adam and Chava to partake of the Eitz HaDa’as. As a consequence, its legs were cut off and the combinations of words detailing the features of tumah of creeping creatures—"כל הולך על גחון"—came to be. In this context, the letter “vav” of "גחון" took on an entirely different meaning.
Since Yisrael lost a good, capable servant when the legs of the nachash were taken away, this sacred role fell to those who possess the wherewithal to support and finance Torah-study. Like Zevulun, the sixth of the shevatim, they would function like a connecting “vav” bound in an intimate relationship with Yissachar, the fifth shevet. Thus, the “vav” of "הולך על גחון" teaches us that it is now incumbent upon Zevulun to fulfill the intended role of the nachash, who is now condemned to crawl on its belly, because it did not wish to fulfill its intended role.
We can now begin to appreciate the message HKB”H is conveying to us by also placing the midpoint of the words of the Torah in this parsha in the words "דרש דרש משה". Fo r, we find the following halachic ruling in the Shulchan Aruch (Y.D., Hilchos Talmud Torah 246, 1):
Every Jew is obligated to study Torah—whether he is poor or rich, whether he is physically able or handicapped, whether he is young or elderly. Even a pauper who goes from door to door, even a man with a wife and children, he must designate times for Torah- study during the day and at night, as it says (Yehoshua 1, 8): “You shall contemplate it day and night.” And someone who is unable to learn, because he does not know how to learn at all, or because he is overburdened, should support others who study. The Rama adds: “It will be considered as if he himself studied. Furthermore, a person can arrange with his fellow that one will study Torah, and the other will support him; and he will split the rewards with him.”
Accordingly, we can posit that the repetitive (double) language—"דרש דרש משה"—is meant to teach us that one who studies Torah should have two people in mind when he is learning and expounding—himself and his Zevulun, who owns part of his Torah. Now, the Moshe in this passuk can be interpreted as a reference to anyone studying Torah. For, we find in the Gemara (Shabbas 101b, Succah 39a, Beitzah 38b) that Torah scholars used to say to one another: "משה שפיר קאמרת" —Moshe, you have spoken well.
