Musar su Salmi 13:78

And so, with the man of lashon hara. When his evil nature is revealed, all hate him, and guard themselves from him, lest he make them objects of shame and humiliation. And even if he merits rising for the resurrection, he will be like an absolute mute. As Chazal have said (Devarim Rabbah 6): "The Holy One Blessed be He is destined to cut off the tongues of the men of lashon hara, as it is written (Psalms 13:4): 'The L-rd will cut off all "smooth" lips, the tongue that speaks boastful things.'" The reference is to the time of the resurrection. Who can fathom the greatness of the suffering of that man and his eternal shame! For then all will know the nature of that man, that he was an evildoer, who, with his smooth lips stirred up hatred between man and his friend, as Scripture states (Koheleth 12:13): "The end of the thing, all is heard," which Onkelos translates: "All the deeds of men are destined to be revealed, etc." For this reason [i.e., that he was a man of lashon hara] this punishment came upon him, that all men rose living and with their speech intact as of yore, and this man, as an absolute mute. From this a man can reflect upon the gravity of the sin, which reaches to his very soul in this world and the next.

The scoffers of that generation maintained that Sarah had been impregnated by Avimelech and that Isaac was the issue. They claimed that, had Abraham been Isaac's father, it would have been impossible for Isaac to have fathered a son such as Esau who pursued married women to commit adultery with them under the noses of their husbands. Isaac's extraordinary success as well as the fact that he was sanctified on Mount Moriah and not allowed to leave the holy soil of ארץ ישראל, all served to show that he was indeed a true son of Abraham. Of Esau the Torah reports in Genesis 36 6: וילך עשו אל ארץ, "Esau went to a land." He had to leave ארץ ישראל because that land "vomits" people who behave in a grossly incestuous manner. Isaac was the model of refinement in every respect. The reason G–d blessed him in such an extraordinary fashion was to demonstrate the fact to one and all that sexually pure conduct unlocks all the bounty of the land of Israel to those who dwell in it.