What is the meaning of "Ach b'Tzelem"?
Rashi citing Menachem: It is the form, like "Ki b'Tzelem Elokim Asah Es ha'Adam 3 " (Bereishis 9:6). Radak - i.e. his form changes from day to day, like a river that turns and flows, and its form changes.
Radak citing Ibn Ezra: It is the arrangement of the stars; they never remain in the same position. So man changes.
Malbim: The reason why the Nefesh was grafted with a body is because man was created b'Tzelem Elokim. Man is an illustration of Elokus that conducts the great world. Just like the body ha'Klali is the great (physical) world, which is under fixed natural laws, and Elokus conducts it via choice, above nature, so the Nefesh can change the nature of the body and make it a new creation. Therefore He gave to it a yearning to ascend from level to level and approach Elokus.
Why does it say "Yis'halech Ish"?
Malbim: Man must always go towards his source without limit. Therefore, there is no limit to the Nefesh's aspirations.
Why does it say "Ach Hevel Yehemayun"?
Radak: They yearn for folly, to gather money.
Malbim: Man made many calculations, and due to his aspirations, he yearns for follies - to gathered imagined acquisitions with no real value.
What is the meaning of "Yitzbor v'Lo Yeda Mi Osfam"?
Ibn Ezra: He gathers money little by little, and he does not know who will take all of it at once when he dies.
Malbim: The wealth that he gathers will not remain with him. In the end, strangers will inherit his toil.
