From Chabad.org: No sooner than the Jews start traveling, and they start complaining. First they complain about the “arduous” journey. Then they grumble about the manna, expressing their desire for meat. Moses turns to G‑d and insists that he cannot bear his leadership role any longer. G‑d tells Moses to gather seventy elders who will assist him in his leadership duties. He also promises to provide the Jews with an abundance of meat — “until it will come out of their noses…” Moses gathers seventy elders and brings them to the Tabernacle where his holy spirit is imparted upon them. Two additional elders, Eldad and Medad, remain in the camp, and the holy spirit descends upon them, too, and they prophesy as well. Joshua is displeased by this, and Moses placates him.
This Aliya is especially troublesome because it contains the Jews’ unfounded complaints to G-d. They complained that they didn’t have meat (although they had plenty of cattle), they suddenly had the urge for some cucumbers, watermelons, leeks, onions and garlic. How random were these sudden urges, and where did they come from? Sifri explains that these vegetables were thought to be bad for nursing mothers, so the Manna that could taste like anything they wanted did not taste like any of these. And why the sudden complaints? This shows the power of reality, of how we can create our own issues and then blame someone else for it. The Jews were looking for something to complain about, and found these silly things. Are we any different? Do we complain about things in our lives (to whomever will listen)? Maybe reading a story like this will make us realize just how silly some complaints really are.