Or celebrate Masechet Avot (Ethics of the Fathers), perek dalet (chapter four), Mishnah Yud Tet (Mishnah nineteen). The Mishnah says: Shmuel HaKatan (the small one) omer (said), Shmuel, the katan, the small one, said. We call him Shmuel HaKatan because, even though he was a great, great person, he had a tremendous amount of humility. He was a very humble individual. He taught, quoting a pasuk (verse) from Mishlei (Proverbs).
The whole Mishnah here is a pasuk from Mishlei: Binfol oyevcha al tismach: “When the enemy of yours falls, don't be happy.” Uvikashlo al yagel libecha: “When he stumbles, don't let your heart rejoice.” Pen yireh Adonai: “Because Hashem may see it.” Vera be'einav: “And it's going to be bad in his eyes.” Veheshiv me'alav apo: “He's going to turn his anger from that person, and he's going to turn it towards you.”
What we're saying over here is that when a person sees the downfall of another individual, even if it's an enemy, even if it's a wicked person, you're not supposed to take pride or be happy when another person is suffering. Human beings are human beings, and even though that person may be an evil individual, we shouldn't look at his downfall and rejoice. We become almost as evil as that person when we're rejoicing at the downfall, at the pain of another individual. So no matter who they are, no matter what they've done, we don't rejoice at their suffering. We can only rejoice in the glorification of Hashem's name when that type of thing happens. And that's what the pasuk also teaches us: when the wicked are destroyed, there's rina, there's a glad song. That's really telling us that we're only rejoicing at the glory of God, but we don't rejoice whatsoever at the pain of another person.
More than that, when we rejoice, it starts to look like we're rejoicing because we think Hashem did it for us, as if we deserve it, as if we deserve the divine intervention of HaKadosh Baruch Hu (the Holy One, Blessed be He). Therefore, that looks bad in Hashem's eyes as well. And at that point in time, if we do rejoice, Hashem turns His anger from that wicked person and will look at us and say, “What are you rejoicing for? You're no better than that individual.” And God forbid, He'll turn His anger towards us.
The pasuk here is all from Mishlei. So why are we quoting it in Shmuel HaKatan's name? Because he would teach it. He would make a point of going over this pasuk over and over again to teach people the lesson: don't be an individual who's happy by the downfall of another person, because many people, especially in his time, were guilty of this type of character trait. They thought it was okay to celebrate the enemy, celebrate the downfall of the enemy, and he came to teach over and over again that that's not the way of the Torah.