Who said this verse?
Rashi: The world officer (the angel Metatron) said it. Yevamos 16b - Hashem did not say it, for He does not age 1 . David did not say it, for he did not live to be so old!
Riva (Bereishis 42:15) holds that Hashem said it; refer to 37:25:3:2. (PF)
Igros Moshe (YD 5:30): Age does not apply to angels that exist forever! (Further, they do not reach higher levels - this is why they are called "Omdim" (Zecharyah 3:7); Chomas Anach ibid., Mishnas R. Aharon 3, p.4). "Zakanti" is a mere metaphor. However, it is improper to say so about Hashem, even as a metaphor. (However, Chazal attribute the appearance of Ziknah to Hashem in Yeshivah (Chagigah 14a; R. Chananel - judgment) and at Matan Torah (Shemos Rabah 28:3)! - PF)
Why does it mention youth and old age?
Radak: I did not see so in my youth, and not in my old age.
Rosh (Bereishis 42:1): From the days of Adam ha'Rishon until the days of Mashi'ach.
What do we learn from "[v'Lo Rai'isi] Tzadik Ne'ezav v'Zaro Mevakesh Lachem"?
Radak: He is totally abandoned, and his minor sons beg for food. A Tzadik might lack, but not a bad lack like Resha'im have. "Ne'ezav" is lacking food and clothing. Yakov requested "v'Nasan Li Lechem Le'echol u'Veged Lilbosh" (Bereishis 28:20), and Hashem had said "Ki Lo E'ezavcha" (ibid., 15).
Riva (Bereishis 28:15): I did not belittle. This is like "Al Ta'ar'uni she'Ani Shecharchores" (Shir ha'Shirim 1:6). I was not pleased that a Tzadik be abandoned and poor - "Le'aves Adam b'Rivo Hashem Lo Ra'ah (Eichah 3:36). Even so, sometimes Tzadikim are poor, like R. Chanina ben Dosa, when they are born with Mazal to be poor.
Rosh (Bereishis 42:1) #1: Hashem establishes at least 30 Tzadikim in every generation. He said about Avraham "Hayo Yihyeh l'Goy Gadol" (Bereishis 18:18); the Gematriya of "Yihyeh" is 30.
Rosh (Bereishis 42:1) #2: Hashem does not abandon Tzadikim at a time of hunger. He prepares from where they will live. He told Eliyahu "Kum Lech Tzarfasah" (Melachim I, 17:9), and at a time of famine, Yakov saw "Ki Yesh Shever b'Mitzrayim" (42:1).
Malbim: If the Tzadik did not succeed, his sons will. (Hashem never abandons both of them.)
