That on the same day that he was created he begot. [Rashi knows this] because it is written, “This is the book of the generations of man on the day...” implying that on the day he was created he had offspring. Accordingly, “On the day,” is attached to “generations of man,” rather than to “He made him in the likeness of Hashem” which follows. For otherwise, why does it say, “On the day Elohim created?” The Torah should have simply written, “The generations of man, in the image of Hashem He made them,” and that would suffice. Perforce, “This is the book of the generations of man” refers back to (4:1), “The man knew his wife, Chavah” and she gave birth to Kayin and Hevel.

Until now he had separated from his wife. Rashi is answering the question: On the day he was created he had children. If so, why did he not have [more] children until now, [one hundred and thirty years later]?

He could easily be induced to turn... Rashi is explaining: Since it is written, “Chanoch walked with Elohim,” we see he was righteous. So why did he die before his time? [The answer is] because “he could easily be induced...”

From whom the world was built up. Rashi is answering the question: Why does it say בן here, and not for other descendants? It simply should have written ויולד את נח. Perforce, בן connotes בנין (building).

He will give us rest. Bereishis Rabbah says: Was Lemech a prophet, that [when Noach was born] he knew about this? R. Shimon ben Yehotzedek said: Noach was born circumcised. For when Hashem cursed the earth, Adam said to Him: O Master of the World! Until when? Hashem told him: Until you beget a circumcised person. Once Noach was born circumcised, they said: He will give us rest! (Divrei Dovid)

If you do not explain it this way then the meaning of the term is not... I.e., if you explain ינחמנו as “he will comfort us,” then its meaning is not related to the name Noach — and the verse says that Lemech named his son Noach because of ינחמנו. For נח [means “rest” and] does not mean “comfort,” so you would have to call him Menachem for the meaning to match the name. And the verse does not say יניח ממנו את מעשינו [although it is closer to “Noach”] because then it would mean that they rested from the work of their hands, and that did not yet happen. They still needed to plow, sow and thresh. Therefore it says that Noach “will bring us rest from... the anguish of our hands,” as he prepared plowing tools for them which they did not have as yet. Why did Rashi not explain, “From our work and the anguish of our hands,” following the order of the verse, but rather put “the anguish of our hands” first? The answer is: “Anguish” refers to the earth’s curse to produce thorns and thistles. And as soon as Noach was born, that curse stopped. But Noach did not make the plow until he grew up. Thus Rashi mentioned “anguish” first, indicating that the verse as well should be understood this way.

I would have to burden him to build many arks. Maharam Yafeh objected: On the contrary, if they would be righteous, together with their wives they would be more than ten and would protect the world, and no arks would be needed! For Rashi explains in Parshas Vayera (18:32) that Avraham did not pray [for Sedom to be saved] for less than ten tzaddikim, since [he knew that] the generation of the Flood had eight tzaddikim, and it did not save their generation. This implies that ten tzaddikim would save their generation. The answer is: Ten tzaddikim would not save the whole generation from the Flood; they would save their city only. Consequently, “I would have to burden him to build many arks” for all the inhabitants of their city, as the Flood would still come and wipe out the rest of the world. (Tzeidah L’Derech)

Of punishable age. You might ask: Rashi already explained what would happen if Noach would have children before the age of five hundred, why was that explanation not sufficient? The answer is: It still needed to be explained what Noach gained by waiting, for if his children would be wicked they too would be destroyed! Thus the second reason is needed, that Noach’s children would not be of punishable age, thus Noach’s merit can save them even if they would be wicked. But all the other people who were not of punishable age were destroyed nonetheless, since they had no [saving] merit. Thus, only one ark was needed. For Noach’s children were not considered righteous just because they were below punishable age — only in Noach’s merit were they saved, which is why Noach did not build a separate ark for each of them.

**And so it was before the Torah was given.**This raises a difficulty: Later, in Parshas Chayei Sarah (23:1), Rashi explains: “When Sarah was one hundred years old, she was like a twenty year old regarding sin.” This implies that from the age of twenty, she was already at a punishable age. Furthermore, Yaakov and his sons did not live to be one hundred and fifty. How could it be that for two thirds of their lives, they were not of punishable age? (*Nachalas Yaakov,*see further explanation there)

First you must discuss... Question: [If so,] why is Yefes not mentioned after Shem, [as he too was righteous]? The answer is: The Torah did not wish to change [the order] too much. Since Shem and Cham were born one after the other, it did not interrupt between them. (Maharshal)