Musar zu Jirmejahu 32:18

Consider the greatness of their punishment. Because of the greatness of their sin, it is almost impossible for Gehinnom to cleanse them of it, as explained in Tanna d'bei Eliyahu 18: "Just as the wicked speak lashon hara, which ascends until the Throne of Glory, so, angels descend from the mouth of the Omnipotent One and take those evildoers and cast them into the [nethermost] depths of Gehinnom. At that time, Gehinnom responds and says to the Holy One Blessed be He: 'Master of the universe, I cannot punish them as much as they deserve to be punished, and the whole world cannot punish them enough. Did this speaker of lashon hara not sin from the earth until the heavens? But first send Your arrows from above, and then they will get from me coals of the broom bush from below, as it is written (Psalms 120:3-4): 'What will He give you and what will He add to you, you tongue of deceit? Sharpened arrows of the Mighty One, together with coals of the broom bush.' 'the Mighty One' is none other than the Holy One Blessed be He, as it is written 'the G-d who is great and mighty, etc.'" (We find the same in Arachin 15b.) And how much must the man of heart strengthen himself and stand guard against this bitter sin, in reflecting upon this awesome punishment, which the great prison house of Gehinnom itself is powerless to inflict unless it also be assisted from above!