Musar su Numeri 23:21

And when we reflect but a little upon this awesome thing, we understand immediately why the Holy One Blessed be He is more severe with this sin than with all others, to the point that He refuses to associate with the man of lashon hara at all to rescue him from his troubles, as will be adduced, please G-d, below in the name of the Sifrei, and as is written in the Zohar, Parshath Shelach: "R. Shimon said: 'The Holy One Blessed be He pardoned all, except lashon hara.'" For it is known that the love of the Holy One Blessed be He for His people, Israel, is exceedingly great, as Scripture states (Jeremiah 31:19): "Is not Ephraim a dear son to me, or a child that I dandle, etc.?" When a man has a dear son or a child that he dandles, and he sees that he is not acting properly, still, he "covers up" for him in his great love for him. And even though he chastises him at times, it will be with compassion and pity. But if some men come to him once or twice and tell him about his sons' waywardness, how he argues and wrangles with people for nothing, how he shames and insults everyone, then certainly he will grow angry with him and beat him and shame him for this. And who caused all this? The teller. The same is true in our case. The Holy One Blessed be He, in His great love for Israel, even though He knows all that is done in secret and in the open (as it is written [Jeremiah 23:24]: "Will a man hide himself, etc.?"), still He will not arouse Himself against them to do them evil, as it is written (Numbers 23:21): "He has seen no iniquity in Jacob" [see Rashi there]. But, if the accuser comes to Him and tells Him of this, He must give him some kind of answer [just as "the kingdom of the earth" must respond when someone cries out before them over some injustice done to him.] For thus has the King of the world established it, that a man's affairs are mediated through defenders and prosecutors.

[And, in my view, this is the intent of the verse (Bamidbar 23:21): "He does not see iniquity in Jacob … the L-rd his G-d is with him": When does He not see iniquity in Jacob? When the L-rd his G-d is with him. But when there is, G-d forbid, lashon hara in Israel, which leads to departure of the Shechinah, as stated in Midrash Rabbah, Parshath Shoftim, then, G-d forbid, He does probe their deeds.]

לא הביט און ביעקב . This is a reminder that even improper thoughts that have not surfaced, i.e. are "within Jacob," have not yet been translated into deeds, are frowned upon. We have elaborated elsewhere on this subject when we discussed the ten directives employed by G–d in creating the universe.