Why does the Torah add the word "l'Soledosam" by Levi exclusively?
Ramban: Because 1 the Torah inserts all of his descendants up to that time, as well as the years that Moshe and Aharon's fathers lived. 2
Oznayim la'Torah: Because although the Torah only lists the family fathers of Reuven and Shimon, 3 it lists also the children of the family fathers of Levi.
Why does the Torah single out Levi, and subsequently Kehas (in 6:18), Amram (6:20) Aharon (6:23) and Elazar (6:25) for special mention?
Ramban: a. In honor of Moshe and Aharon; and b. because in their own right they were distinguished pious men. Also refer to 6:20:1:1.
Seforno: Because Levi, who lived longer than all his brothers, and subsequently Kehas and Amram, taught their children 'Torah' to the extent that Moshe, Aharon and Miriam came from them; Aharon, who went on to marry the sister of the esteemed Nachshon, fathered leaders of the generation, 1 who would later be chosen as Kohanim, and Elazar took as a wife a daughter of Puti'el, 2 also an esteemed leader of that generation, and fathered Pinchas, who merited a covenant of peace.
Rashbam: In presenting the entire chronology of the world from Adam through to the second Beis-ha'Mikdash (inclusive), the Torah lists the years from Adam to Noach and from Noach to Avraham (in detail); then it lists the years of Avraham, Yitzchak, Yaakov, Levi, Kehas, Amram, Moshe, Yehoshua and the Shoftim; the kings, the seventy years of Galus Bavel and the years of the second Beis-ha'Mikdash (in Daniel).
Targum Yonasan: Because each one merited to have children who were Tzadikim and lived a long time until they saw righteous offspring - Levi lived to see Moshe and Aharon; 3 Kehas lived to see Pinchas (alias Eliyahu Kohen Gadol), who will take Yisrael out of Galus in the time of Mashi'ach; Amram, who married his righteous aunt Yocheved, besides fathering Aharon and Moshe, lived to see the sons of Rechavya, the son of Gershom ben Moshe, and Aharon, who married Elisheva bas Aminadav, the sister of Nachshon, who bore him Nadav and Avihu, Elazar and Isamar.
Why does the Torah tell us how long Levi lived?
Rashi: To enable us to calculate 1 the years of slavery - which only began after the last son of Yaakov died; and the last of Yaakov's sons to die was Levi.
Refer to 6:16:3.1:1 for details.
QUESTIONS ON RASHI
Rashi writes: "'The years of Levi's life' - [are stated,] to teach you the duration of the slavery; for as long was one as the Tribes still lived, they were not [yet] enslaved...." How should these years be calculated?
Gur Aryeh (also see Riva to 6:14): Levi was 43 years old when he went down to Egypt. (His younger brother Yosef was born to Rachel, at the same time Dinah was born seventh to Leah - at the close of the seven years that Yaakov worked for Lavan after his marriages. Levi was born third to Leah - presumably in her third year of marriage to Yaakov. Hence, Levi was 4 years older than Yosef. If Yosef was 30 years old when he stood before Pharaoh, followed by 7 years of plenty and 2 years of famine; then when Yaakov and his sons descended to Egypt, Yosef was 39, and Levi was 43.) We see from our Pasuk that Levi lived another 94 years in Egypt. If Bnei Yisrael were in Egypt for 210 years, 1 then their slavery lasted for at most 116 years.
See Rashi to Bereishis 42:2, and to Shemos 12:40.
Rashi writes: "... As long as one as the Tribes still lived, they were not [yet] enslaved...." Why were the Egyptians unable to enslave the Bnei Yisrael during their lifetimes?
Maharal (Gevuros Hashem Ch. 9, p. 54): Yaakov and his sons were not themselves worthy of being enslaved; only that they were part of the significant number of 70 souls. Refer to 1:5:1.02:1; and to 1:6:1.1:1.
Rashi writes: "... As long was one as the Tribes still lived, they were not [yet] enslaved...." But elsewhere, Rashi writes (to Bereishis 47:28) that as soon as Yaakov passed away, the Egyptians began to subjugate them!
Gur Aryeh (to Bereishis 47:28); Maharal (Gevuros Hashem, beg. Ch. 12, p. 64): The Egyptians did begin to subjugate the Bnei Yisrael upon Yaakov's death; albeit not consistently. Only after Levi's death were they made slaves on a permanent basis. 1
Maharal: The Mitzrim cunningly introduced the slavery gradually, in stages; refer to 1:14:151.3:1 and 1:14:151.4:1.