(1) Everyone on earth had the same language and the same words. (2) And as they migrated from the east, they came upon a valley in the land of Shinar and settled there. (3) They said to one another, “Come, let us make bricks and burn them hard.”—Brick served them as stone, and bitumen served them as mortar.— (4) And they said, “Come, let us build us a city, and a tower with its top in the sky, to make a name for ourselves; else we shall be scattered all over the world.” (5) GOD came down to look at the city and tower that the mortals had built, (6) and GOD said, “If, as one people with one language for all, this is how they have begun to act, then nothing that they may propose to do will be out of their reach. (7) Let us, then, go down and confound their speech there, so that they shall not understand one another’s speech.”

(1) ...One language - that is what caused the first sin. This is that they agreed to stop in one single place. And this is against the will of God that said to "fill the land and replenish it" - that is, to walk to all its places, since the land was created to be settled.

(2) ...And the same words - The text did not explain what those words were, rather, it leaves as a hint, as explained in midrashim. But the words themselves are not explained by the text, it just tells us that they were the same words, to teach us that it wasn't because of the content of the words themselves that the Holy One of Blessing was distressed. They were what they were, and in its simplicity there is not sin, and on the contrary all appears well. But here what happened is that all thought the same thing, and this came to be the problem of the settlement.

(1) Burn them thoroughly - There is no place in the Text where something is told that has no impact in the story [therefore, ask:] Why do I care if they were using stones; bricks; were constructing using wood; or made their brick by burning? Even before the Flood it is written "and afterward he build a city" (Genesis 4:17)! And it appears that here there is a hint regarding our sages' tradition that Avraham Avinu was thrown in the fiery furnace - ... But from here we have a hint to the issue of what obviously was happening before the tradition saying that they threw Avraham Avinu into the fiery furnace: they did not make the furnace for this need [to burn people], rather this was the fiery furnace (in Daniel, see Dan. 3:6) done for the need of people [to fire bricks]. And the Text is informing that this furnace was for the need of the city and the tower, and from this we understand how big and deep was this furnace, and from this furnace Avraham Avinu was saved.

(1) And its top in the sky - It is obvious that you should not think that this would be one city to the whole world, rather they thought that the other nearby cities would be subjects to that city that had the tower, that they would be able to see from it to the distance, over all their settlement, so that no one would be able to separate themselves and go to another land. That's why they needed its top reaching the sky.

(2) And we will make a name for ourselves - people were set up to watch אנשים משגיחים and be in charge of the thing, and they were army chiefs in charge of punishing those who would cross, since if this is not the case there would be no need for the tower. And all that was due to fear/suspicion.

(3) Lest we be scattered over all the face of the earth - However, we must understand why they feared that someone might leave to another land. And it is understood that this was related to the uniformity that was among them. And since the opinions of people are not identical, they feared that people might abandon this philosophy and adopt another. Therefore they sought to ensure that no one would leave their society. And one who veered from this uniformity among them was judged with burning, just as they did to our forefather Abraham. And the "same words" can also be seen as the fact that they would kill whoever did not think like them. And more is explained on verse 6. (1) They are one people. The explanation of "people" is that they all follow one custom [minhag], as it is written later on Gen. 28:3 in the explanation of 'and you shall be a congregation of peoples'. (2) If this they began to do. This is but the beginning of the transgression: they want to remain in one place. (3) And now nothing will be withholden from them which they purpose to do. If they finish the tower they will come to a second thought, to prevent by force other thoughts than this one. And this is a thing [that brings] killing, and violent destruction of the settlement, and it does not help that at this moment they are together with one opinion.

“And you shall become an assembly of peoples” (Genesis 28:3)

An assembly (kahal) consists of ten, as stated in Ketubot 7b. The word peoples (amim) refers to groups distinguishable from one another by their different ways of life, so that each is considered a people unto itself—even though they are all governed by a single authority. ....

God therefore told Jacob that his descendants would become ten peoples. That is, each tribe would possess its own customs and constitute a people unto itself. Although they would all share one Torah and one king, they would nevertheless differ in their ways of conducting worldly life.

...

(1) This Book commonly known as The Book of Bereishis, is referred to by the Prophets as Sefer HaYashar, the Book of the Upright, ...

(3) [The meaning of] yashar is as described in the Song of Ha’azenu:
The Rock - perfect is His work, for all His paths are justice; a faithful God without injustice - righteous and yashar is He.
By praising [God as] yashar, [the Torah] acknowledges the Holy One blessed be He’s judgment to be weighed against a generation [such as those who would] live during the destruction of the Second Temple, who are described as a perverse and twisted generation. We explained [ad loc], though they were righteous and pious, toiling in Torah study, they were not upright in their societal behavior. And so due to the baseless hatred for one another residing within their hearts, they suspected anyone who was not religious in accordance with their viewpoint to be a Sadducee or heretic. [This deficiency in the Torah scholars’ character] led to rampant murder along with a transgression of all the other evils in the world, causing the Temple’s destruction. [This is how the Torah presents] the acknowledgment of God’s justice [here]: the Holy One blessed be He is yashar, being intolerant of those types of [distorted] righteous individuals. [He is only accepting] of those who act in a way that is socially yashar – unlike those who act in a perverse manner, even when their actions are performed for the sake of Heaven. As such [a deficiency] can lead to the destruction of [God’s] creation and the ruin of civilization. (4) This was the greatness of our forefathers. In addition to being righteous, pious, and lovers of God to the utmost degree, they were also yesharim. That means they were civil with the [other] nations of the world, despite [the latter] being detestable idol worshipers. Our forefathers nevertheless extended them love and concern for their welfare, as this fortifies [God’s] creation.
[To illustrate,] we see how our forefather Avraham exerted himself greatly in prayer for the welfare of Sodom. He desired their survival, even though he totally detested them and their king due to their evil ways (as is clear from how he spoke to the King of Sodom). In the Midrash Rabbah on Parashas Vayerah, (Parasha 49) we find the following about this:
The Holy One Blessed Be He said to our forefather Avraham, “You love righteousness and loathe wickedness. You love to vindicate My creations and you loathe to convict them.”
He literally was like the father of a multitude of nations. For even when one’s son is not walking in righteousness, [the father still] seeks out his wellbeing and benefit. Similarly did graciousness and the most remarkable civility abound within Avraham’s words to Lot, as will become clear in the parashah of Lech L’cha....

This behavior is that which sustains the world, which is in turn a theme particular to this Book, the Book of Creation. For this reason this book is also entitled Sefer Ha-Yashar, highlighting this aspect of our forefathers’ actions. (5) ... (6) We have explained well why this book is entitled, Sefer HaYashar, being the Book of Creation.