The Yismach Moshe (Bereishis יקרו מה ולי י"א ה"ד) teaches in the name of the Baal Ha'Ikrim that for all parts of creation, the Torah writes, וירא אלקים כי טוב, "And Hashem saw that it was good." But for the creation of man, the Torah doesn't write וירא אלקים כי טוב. This is because man wasn't created טוב. He becomes "good" after he passes tests and betters himself. Hashem said (Bereishis 1:26) נעשה אדם, "Let us make man." Why is נעשה written in plural? It is because man was created together with mankind. Hashem's creation of man isn't complete until human beings pass tests. This is when the creation of man is completed.
Rebbe of Liska (אך פרי תבואה, בפרשתן) repeats this lesson, which he heard directly from the Yismach Moshe. He adds that the creation of a Yid alone isn't complete because he is destined to become far better and greater than he was at the time he was born. About the goyim, it states עם הדומה לחמור, a nation similar to a donkey. They are like animals; they don't need growth, so they were completed at the beginning of creation. אך פרי תבואה adds that this can explain the names of יעקב and עשו. On the words (25:25) ויקראו שמו עשו, "And they called him עשו" Rashi writes, "Everyone called him this way...
