창세기 7:8의 Musar

ויהי ביום השמיני . Our sages (Bereshit Rabbah 42,4) have taught us a rule that whenever the Torah uses the expression ויהי, this is a reference to a painful experience. The sages are sometimes hard-pressed to demonstrate the validity of this dictum. Our question is why the Torah chooses to use an expression which points at something unpleasant when we are taught that elsewhere (Genesis 7,2) the Torah spent additional verbiage such as הבהמה אשר לא טהורה, "a category of animal which is not ritually pure," instead of simply saying בהמה טמאה, "an impure animal," merely to avoid referring expressly to something unpleasant?

And our Rabbis said (Pesachim 3a), “A person should never put out a disgraceful matter from his mouth; as a verse was distorted by eight letters rather than have it put out a disgraceful matter, as it is stated (Genesis 7:8), ‘From the pure animals and from the animals that are not pure.’” For at that time, the impure animals were permissible to eat but not pure for a sacrifice. Hence it is considered a disgraceful expression if one disgraces things that are for human food. And see that a man must be careful not to put out a disgraceful matter from his mouth - even if by his leaving it, it will bring him to speak at length and add to his statements. And it is like a fence to be careful from vulgar speech - which is one of the weighty sins. And [it is] also a fence from speaking evil speech and the placing of defects upon the creatures - as our Rabbis, may their memory be blessed, have said about the distancing of [disgraceful] speech (Bava Batra 123a), “The verse did not even speak in disgrace of impure animals.” And our Rabbis said (Pesachim 3b) that one of the priests said in front of Rabban Yochanan ben Zakkai, “I received [for] my portion, the size of a lizard’s tail.” They investigated his background, and they found a trace of disqualification about him.
And our Rabbis also said (Pesachim 3a) that a person must choose an honorable phrase [instead of using] a dishonorable phrase - even if it is not disgraceful - whether it is in words of Torah or in speaking about matters of the world. And this is so long as he does not speak at length for its sake when speaking words of Torah. For a person is obligated to teach his students in a terse fashion. And the matter of honorable phrases is the path of words and speech that was tread upon by those of clean intellect and those that speak with clarity. And they weigh and know which phrase is honorable and which is its opposite, as it is stated (Job 15:5), “And you choose the language of the crafty.” And it is stated (Job 33:3), “and that which my lips know they shall speak sincerely.” And it is stated (Proverbs 1:20), “The tongue of a righteous man is choice silver.”

Another problem is the meaning of the word במרמה, if meant in the sense of חכמה, as Rashi says. If Isaac wanted to use the word in that sense, why did he not say: בא אחיך בחכמה, instead of using the word מרמה? Our sages in Pessachim 3 explained that the Torah distorted eight letters in Genesis 7,8 in order not to have to use gross language such as the word בהמה טמאה. Why do we not find the same here? The Torah could have used the word חכמה in order to avoid the negative connotation of מרמה, deceit?