Our Parsha begins with a description of the Mitzvah to light the Menorah in the Mishkan (במדבר ח;ב). Chazal understand that the Posuk means to say that when the six lights (three on each side) would be kindled facing the center of the Menorah as the Torah requires (שם), the seventh one, the one in the middle, would only then be lit.
Rabbi Raphael Pelcovitz, in commenting on the Sforno's remarks about this Posuk, explains a Posuk in Mishlei (ג;ט"ז) which says concerning wisdom, אורך ימים בימינה בשמאלה עושר וכבוד, length of days is in her right hand and riches and honor are in her left hand. He notes that the Gemara in Shabbos (דף ס"ג.) interprets this Posuk as saying that those who pursue eternal life, by engaging in Torah study, are considered as the right hand, presumably because Torah study, when done seriously, is physically draining, and requires all of one's strength, represented by the right hand. These people are promised אורך ימים, length of days, as the reward. This is fitting because the life goal of such people is to understand the ways of Hashem to the best of their ability, and thus the more time that they have, the better they will be able to achieve this goal. On the other hand, those who occupy themselves with more material matters, but nonetheless lend their financial support to the students of Torah, are blessed with עושר וכבוד, more riches and honor, again a reward very appropriate for their endeavors.
The Gemara in Chulin (דף צ"ב.) compares the Torah scholars to grapes and those who support Torah to the leaves which protect the grapes. This is because the Torah itself, because of its sweetness, is compared to wine; the Talmidei Chachamim who produce the Torah are likened to the grapes which produce the wine. Those who support the Talmidei Chachamim are thus like the leaves which protect the grapes, and indeed through photosynthesis, give the grapes their nutrients. The Gemara therefore says that the grapes should pray for the leaves because without the leaves, the grapes could not exist. Without the supporters of Torah, the Talmidei Chachamim could not exist, because they would, by necessity, have to go out into the business world and be exposed to various distractions and temptations, similar to the harsh elements the grapes would have to face if not protected by the leaves.
Using this idea, the Sforno says that the middle of the Menorah represents the Divine light of Hashem. Only with those on the left, the supporters of Torah, and those on the right, the Torah scholars, working together will we merit seeing and understanding the Divine light. This cooperation is referred to by Chazal as the Yissochar - Zevulun partnership, and only a healthy relationship will produce the desired result. Avodas Hashem is our primary task in this world, and only with cooperation will we successfully achieve our aspirations. The Sforno points to the Posuk which describes Maamad Har Sinai (שמות י"ט;ח) and says that the people answered together, and said that they would obey all that Hashem asked of them. Only together can we fully fulfill Hashem's desires for us.
Rabbi Pelcovitz then adds that earlier in the Torah, in Parshas Terumah, we also find a description of the Menorah (שמות כ"ה; ל"א-מ'). There, the Sforno explains that one side of the Menorah represents the learning of Torah with its intricate analysis and details, while the other side represents applying the concepts one has learned and turning them into deeds. There too, the unity of both sides is needed. One may ask, though, why the Sforno, although emphasizing unity in both places, changes the nature of his message. In Parshas Terumah, he stresses one type of unity, as it relates to Torah as the word of Hashem, while in our Parsha, he emphasizes unity as it relates to the Jewish people and their involvement in Torah. Why the distinction?
In Parshas Terumah, the discussion is about the building of the Menorah; in our Parsha the discussion is about lighting, mentioning only one physical aspect: the fact that the Menorah was chiseled out of one solid piece, also hinting at unity. Therefore, in Parshas Terumah, where the emphasis is on building the Mishkan to serve Hashem, the Sforno explains the Menorah in a way that the unity of Torah, Hashem's word, is stressed. We are thus taught there how to serve Hashem through Torah. In our Parsha, the emphasis is instead on man's involvement, specifically Aharon's role as the Kohein Gadol, the person who loved all the Jewish people, and who perhaps better than anyone else, could unite them. The Sforno thus explains the Menorah here in a way that the unity of the people, through Torah study and Torah support is stressed.