In parshas Shemos we read that Moshe struck down an Egyptian taskmaster that was beating a Jewish slave and hid him in the sand, thinking that nobody knew. The next day he saw two Jews quarreling (Dasan and Aviram), one raised his hand to hit the other. Moshe said to him, "Why do you strike your friend?" The man retorted, "Who appointed you as a leader and judge over us, do you intend to kill me as you killed the Egyptian?!" Moshe was afraid, he said, "so the fact is known."
The Midrash tells us, that Moshe said, "you have lashon hara (evil speech) between you, how are you worthy of redemption?"
It seems from here, that Moshe felt, that lashon hara alone, was enough to hold off the redemption from Egypt.
Our sages compare lashon hara to some of the worst sins, from denying G-d's existence, to the big three, idolatry, adultery and murder.
However, we know that among those that left Egypt, there were idolaters, but that didn't stop the redemption. So we have to understand, what is it about lashon hara, that is so egregious, that it alone could hold up the redemption?
When it comes to war, we see a similar differentiation. The Talmud Yerushalmi tells us, that "David's generation were all tzadikim (righteous), but because they had informers, they would go out to war and fall (in battle). Achav's generation were idolaters, but because they didn't have informers, they would go down to war and be victorious." What we see from this, is that when it comes to war, unity and peacefulness brings victory. However, we still have to understand, what is it about lashon hara, that holds up the redemption?
Rashi explains the words, "So the fact is known," from a second Midrash, that Moshe was saying, that now he knows why they are in exile. In other words, not only does lashon hara hold back the redemption, but it is also the reason for the exile.
In the words of Dasan and Aviram to Moshe there was far worse than lashon hara, they were threatening to inform on him to the Pharaoh, which they did, and informing, in this case, is much worse than plain lashon hara. But from the Midrash and Rashi, it seems that Moshe wasn't as bothered by that, as he was by the lashon hara. Why is lashon hara worse?
With the redemption from Egypt we became a nation of our own, as it says about the Exodus, that Hashem took for himself "a nation from within (another) nation." The defining factor of a nation is that the people are united, and what unites us as a nation is far greater and more powerful than any other nation, as will be explained.
The Rambam calls us a nation even before the Exodus, but what he is referring to, is what makes every nation a nation, that they are united with common ideals and purpose. The problem with this is, that when their ideals change or their purpose becomes irrelevant they lose their identity as a people. As he explains, that being the children of Avraham, Yitzchak and Yaakov, whose purpose was to teach the world about G-d, we were "a people that knew G-d," in other words, that was our ideal and our identity as a nation. However, the Rambam continues to say, that in Egypt many were influenced and entrenched in the Egyptian culture. He concludes that "out of Hashem's love for us, and to keep the promise he made to Avraham our forefather. . . Hashem chose Israel as his (nachala) portion. . ."
From the last words of the Rambam, the difference between the kind of nation we were before the Exodus and after the Exodus becomes clear. In Egypt, we were united under a common ideal, but Hashem took us out of Egypt because He chose us, we became a nation based on something greater than any human ideal, we are united because Hashem chose us to be his nachala. What is a nachala?
A nachala refers to the portion of land that was given to the Jewish people upon conquering the land after the Exodus. By law, the portion of land that was given to a family, was to stay in the family forever. In other words, when Hashem chose us to be his nachala, it means that we became His nation forever. This uniting factor, being from Hashem is not subject to change.
True choice is not based on the items being chosen, but on the one who is choosing. If it is based on the items, you will always choose the one you think is better. That is not true choice, that is called being smart. However, when the items are exactly the same, and you choose one, that is true choice.
When Hashem chooses, it is always true choice, and he chose us as His nation. Which includes all of us, from the most righteous to the least. That is why even idolaters went out of Egypt, because they were also part of the nation that Hashem chose. The only thing is that we had to be united, because if we weren't, then there would be no nation for Hashem to choose. So the only thing that would hold up the redemption is disunity.
There are several negative aspects of lashon hara.
The first is the damage it does, as "The sages say, 'lashon hara kills Three. The one spoken about, the listener and the speaker.'"
The second is the bad it brings out in the person who is spoken about, because until it was said, it was hidden.
These two aspects are destructive and hurtful, but like other sins, they don't breed disunity.
But there is a third dimension, and that is lashon hara itself. Even if the person speaking has no intention to cause damage, or to tell of the negative aspects of his friend, and even if he doesn't speak out of hate, the mere fact that someone talks badly of another, shows that there is disunity. And as mentioned earlier, when there is disunity, there is no nation for Hashem to choose, and by extension, there is no redemption possible.
Now we can understand why lashon hara is so bad, and why it bothered Moshe so much, because it itself could hold up the redemption.
This will help us understand why by the Seder, one of the four sons we speak of, is the wicked son. You may ask, why include the wicked son? The answer is, that without him, we aren't complete, meaning, there is no nation to redeem.
The unity of the Jewish people, is what caused the redemption from Egypt, and it is the same unity that will bring the future redemption. May it come soon.