The Bet Halevi quotes the Gemarah in Mesechet Menachot 29:
(Of) The four species of the Lulav, two of them have fruit (the etrog and the palm), and two of them do not have fruit (the Aravah and the Hasadim)
Having or not having fruit symbolizes the productive Jew versus the Jew that is not productive.
Nonetheless, one does not fulfill his obligation unless they are all together in Agudah Achat/ One group. So too, the Jewish people must be together in order for God to be happy with them.
Regarding the Mitzvah of Lulav, this Gemarah says that the ones that have fruit need the ones that do not have fruit, and the same is true for the Jewish people. The pasuk is quoted: “God builds in the heavens, V’Agudato/and His bundle has a foundation on the ground.”
The Gemarah explains this to mean that it is only when there is a foundation of unity and Agudah/a bundle, that God builds in the heavens. This concept is actually referred to in our Rosh Hashanah prayers. The Daat Zekenim, (Vayikrah 23,40) quotes from our prayers, where we say, UBechen, Ten Pachdecha… when we are asking Hashem to instill His fear into the world, and we end off with a prayer that everyone should make Agudah Achat/one group to do the Will of Hashem.
There is an organization called Agudat Yisrael, and that name comes from this pasuk and from this Gemarah that We want to have an Agudah.
The sefer Pardes Yosef
(Bereshit 49,1) says something fascinating:
There is a pasuk in Re’eh (14,1) בָּנִים אַתֶּם לַה׳ אֱלֹקיכֶם לֹא תִתְגֹּדְדוּ
You are children to Hashem your God, Don’t make separate groups
This is a Halacha. You can’t have a synagogue with different customs within it.
It can’t be that half the shul answers Kaddish one way, and the other half answers another way.
It can’t be that half the shul wears their tefilin on Hol HaMoed and half do not. Each shul can have their own customs, but in one shul, to have different groups is divisiveness. That is against the Halacha of לֹא תִתְגֹּדְדוּ/Do not make separate groups.
The sefer asks what the connection is between the two halves of this pasuk:
You’re children of Hashem,
Don’t make separate groupings
And he explains that the Jewish people are referred to both as children and servants of God, as we say on Rosh Hashanah in Hayom Harat Olam:
Im K’Banim, Im K’Avadim
God will decide whether to treat us like children or like servants. We want to be treated like children. Children obviously get preferential treatment.
And when the Jewish people are in one grouping together, then we are considered children. But when we are separated, and not getting along like brothers, then we cannot be considered children.
We can’t have it both ways. If Hashem is my Father, and Hashem is his Father, that makes us brothers. But if we aren’t brothers, than Hashem can not be our parent.
So a lack of unity indicates a lack of being sons of Hashem. Therefore, we say that if we want God to treat us like sons, we have to be like brothers. That’s what it means:
לֹא תִתְגֹּדְדו/don’t make separate groups, but rather be
Agudah Achat/one group.
Have a wonderful day.