לאבן, “as stone.” The letter ל is vocalised with a semi vowel, sh’va, not with a kametz.

והחמר היה להם לחומר, “and the bitumen served them as mortar.” They mixed it with pitch in order to make it waterproof. The pitch here is called chemor.

וראשו בשמים, “with its top in the sky.” This is obviously an exaggeration, a figure of speech. The Torah uses such exaggerations when describing Canaanite cities as “fortified into the sky,” (Deuteronomy 1,28) We must not forget that the term: שמים, sometimes refers to spiritual concepts, as in “celestial spheres, whereas on other occasions it refers to the horizon, or outer space. Birds are sometimes described as flying, בשמים, obviously not “in the heavens,” but “in the air.”

ונעשה לנו שם, “and let us make a name for ourselves.” They referred to establishing a reputation of grandeur vis a vis any other creatures. [I do not understand with which other creatures they wanted to compete, as man was the supreme creature on earth. Ed.]

פן נפוץ, “lest we scatter.” They were afraid that war might break out among them, assuming there were competing nations or human beings in distant areas unknown to them. At any rate, they realised that strength lay in numbers and in visibility over vast distances, such as the top of a tower that can be seen from afar. Basically, they felt that if they were to obey G-d’s command “to fill the earth,” this would contribute to their becoming ineffective in competition with G-d.

וזה התלם לעשות, “and this is what they have begun to do.” The letter ה in the word hachilom has the vowel patach under it.

ועתה לא יבצר, “and now that they all know seventy tongues, unless they will be scattered they cannot be prevented from translating their evil design into action.” [By dispersing them, they will forget the other tongues, and this will make unity harder for them to maintain. [This interpretation is first found in B’chor shor, one of the Tossaphists, Rabbi Yoseph. Ed.]

ונבלה, “let us confuse, etc.” the word is closely related to בלולה, “thoroughly mixed.”

אשר לא ישמעו איש את שפת רעהו, so that they will not understand one another’s language.” They will forget any tongue other than the one they are in the habit of using. The seventy tongues will remain their collective property, but not everyone will be able to speak all these tongues. No new tongues came into existence at this time.

אלה תולדות שם, “These are the descendants of Shem;” whenever a paragraph commences with the word: אלה, this is to alert us that it is not a continuation of what had preceded it. In this instance, the Torah wishes to distinguish between the evil people featured in the previous paragraph and the good people, whose descendants followed their illustrious ancestors.

ויחי שם אחרי הולידו את ארפכשד, “After having sired Arpachshad, Shem lived for another 500 years.” The formula preceding the death of the members of the earlier generations familiar to us as: ויהיו כל ימיו, “all of the years of his life were, etc.,” is absent now seeing that the life-spans of the antediluvian generations had closely approached 1000 years, something no longer the case after the deluge. (Compare Psalms 90,5 זרמתם שנה, “You let their years flow past as if they had only slept.” According to David, normal life spans in his time amounted to 70, maximum 80 years; verse 10 in the same chapter) There was therefore no need for the Torah to add the words: “all their days.”

ויולד בנים ובנות, “he sired sons and daughters.” The earth filled up with human beings after the deluge, According to an opinion quoted in Bereshit Rabbah as well as in Sanhedrin 69, it was not unusual for eight year olds to be able to ejaculate semen which produced fetuses. When people who had left behind adult children died, their death is often described as שכיבה, “lying down,” whereas when they did not leave behind adult children they are described as “having died,” i.e. וימת. An example of the former is King David, (Kings I 2,10), whereas an example of the latter is his uncle Yoav, or, according to a different manuscript, Job, who did not leave behind adult sons.

יסכה, according to Rash,i this is another name for Sarah. If So, Haran must have sired her when he was only 6 years old, according to the list of the names of Terach’s children. Avraham was supposed to have been a year older than Nachor, whereas Nachor was a year older than Haran, which means that Avraham was two years older than Haran. When we allow a year until Milkah and her sister Yiskah each were born, and we know that Avraham was 10 years older than Sarah from the Torah’s own report, it follows that Haran could not have been older than 8 years when Sarah was born. Allowing for the pregnancies preceding the birth of Milkah and Yiskah, Haran could not have been older than 6 years when he slept with his wife. (Bereshit Rabbah 38,14) Other examples of products of such early unions are Betzalel and Bat Sheva, as well as Er and Onan, sons of Yehudah, son of Yaakov. (Compare Sanhedrin 69)

עקרה, אין לה ולד, whereas originally she had not even had a womb, by the time she became pregnant with Yitzchok she had grown a womb.

ויקח תרח את אברם בנו, Terach took his son Avram, etc;” he intended to take him all the way to the land of Canaan, seeing that he was descended from Shem and that land had been given by G-d to the descendants of Shem as we know from Genesis 9,27. Lot and Sarai went with Terach, seeing they were the survivors of Haran’s family.

ויצאו אתם מאור כשדים, “they emigrated with them from Ur of the Chaldeans at the command of G-d.” The basis for this interpretation is found in Genesis 15,7, where G-d is quoted as telling Avraham: “I am the Lord Who has taken you out of Ur Casdim;” (not Terach). According to this interpretation, we do not know precisely where G-d had told Avram to leave Ur Casdim. The author of this interpretation is Ibn Ezra.

ויבאו עד הרן, “they came as far as Charan.” Terach was not able to complete the journey all the way to the land of Canaan, and died in Charan.