What is "Kol Asher Ya'aseh ha'Elokim [Hu Yihyeh l'Olam]"?
Rashi: It is everything that He made in Ma'ase Bereishis.
Rashbam: All the times that are in His hand.
Ri Kara: All that Hashem does, that one toils and another consumes it, so is proper to be always.
Rid: Even though there is no gain from man's deeds, for time changes on him and his deeds, Hashem's deeds last forever. He and His deeds do not change, only if He desires [to change His deeds].
Seforno: It is what Hashem did without an intermediary, i.e. kinds of creations. [The species] never cease - "Ki Hu Tzivah v'Nivra'u; va'Ya'amidem la'Ad l'Olam" (Tehilim 148:5-6). Their existence is not influenced via any created being, only from Hashem.
Metzudas David: It will always be in the amount that Hashem bounded.
Why does it say "Alav Ein Lehosif u'Mimenu Ein Ligro'a"?
Ri Kara: Do not say that it is proper that a person live long enough to consume his wealth, and others will not consume his exertion. Do not say that his days should be diminished from what was allotted 1 to him, for in diminished days he will consume his toil.
Seforno: Hashem did not lack any knowledge that would detract from their perfection and require fixing.
Metzudas David: No one can increase or decrease the Shi'ur that Hashem fixed.
What do we learn from "veha'Elokim Asah she'Yir'u mi'Lefanav"?
Brachos 55a: A bad dream 1 is worse for the body than lashes (for it makes one worry).
Brachos 59a: Hashem made thunder to straighten crookedness of the heart.
Shabbos 31b: Hashem made the world solely in order that people will fear Him.
Rav Sadya Gaon: Hashem already commanded to fear Him.
Rashi: When Hashem changes [nature], it is in order that people will fear Him 2 . For seven days [before the Mabul], the sun rose in the west and set in the east, so that they would fear Him [and repent - Avos d'R. Nasan 32:1). The ocean breached its boundary in the generation of Enosh and flooded a third of the world (Tanchuma Noach 18), the sun went back 10 steps in the days of Chizkiyah (Melachim II, 20:11), and in the days of his father Achaz (the day that he died), the day was shortened and the night lengthened, so he would not be eulogized (Sanhedrin 96a). All this is so people will fear Him! Therefore, one should engage only in Mitzvos, and fear Him.
Ibn Ezra: Hashem made that people cannot add to His deeds or detract from them, in order that they will fear Him.
Rashbam: He made times of evil and of good, in order that people will fear Him and repent.
Ri Kara: Hashem made that one toils and another consumes it, in order that people will fear Him. One will say, my days are few; if I do not give today from my property to Aniyim, and acquire the world to come, when will I do so?! Tomorrow I will die, and others will consume my property! If people lived long, they would not think so.
Rid: He made that times change and people die. If not, many would not fear the Creator.
Metzudas David: Hashem did not fix the Shi'ur for His benefit, only in order that people will fear Him and not rebel against His mouth. It is the exact Shi'ur to bring to fear, even if we do not know it due to our limited knowledge.
