As usual, his words have a meaning behind them, and there are two meanings; the obvious, and
the hidden. The obvious plainly seen message being that all of the Israelites stand before G-d ready to enter His covenant, so it will take all of them to hold it together. All of them must come together as individuals no matter if they’re elders, tribal heads, or officials to form a whole to serve G-d or He will
tear them down.

The second message Moses is sending is much subtler but much more important. He’s telling the
Israelites that the Jewish part of their lives must encompass all other parts of their lives in their entirety. He commands them to pull together the different parts of their lives, from their role as a
tribal leader to being a judge, to just being simply a householder in Israel with God’s laws and live them accordingly. Moses tells them to do this because if they only live a half-life, the covenant will fall apart as we see later in history. As one tries to live a double life the two tend to contradict each other
and pull each other apart. If all the Jews are being pulled apart individually, not only will they forget about G-d they will pull their own society apart.