Gemara:


Ein Ayah: The individual and the world are similar in the way they must act to achieve shleimut (completeness). A person has good and bad powers. If the bad powers will be totally prevented from finding expression, many good things will be missing because they require the strength and persistence that the bad powers provide. However, if they find expression without any inhibiting factors, they will pass all boundaries and bring the world to a very corrupted state. The Torah hints at this in the story of Yaakov and Eisav. Eisav, who possessed coarse powers, actually was born first. Yaakov did not prevent his birth, but his hand grasped Eisav’s heel, representing that Yaakov would not allow Eisav to go as he liked without boundaries.
When the bad powers become actualized, it is not enough that the good powers will set boundaries for them. Rather, the main thing is for the bad to have to follow the dictates of the good, with the latter enjoying dominion. That happens when one has shleimut, with all the accompanying grandeur. This idea of dominion is the content of the name, Yisrael, which Yaakov received later, as the pasuk explains, "For you have shown dominion among angels and men" (Bereishit 32:28).
Even when good will be busy organizing the actions of the bad powers, some type of muzzle and leash need to remain so that the border will not be breached and allow bad’s existence to become too strong. If it will be too strong, it will cease to follow the directives of the good powers. This is why Yaakov must exist, although secondary to Yisrael.
In matters of the world as well, it is impossible for the world to reach its full potential of grandeur without strengthening even the physical powers. This includes the lowest powers that are brought by those who lack the wisdom to hold on to good and strive for true shleimut. The power of Israel, who publicized knowledge of Hashem and His ways, which are charity, justice, and kindness in the world, places a muzzle. This prevents bad from continuously strengthening itself, which would negate man’s noble spirit.
When Yisrael is in exile, it acts in a hidden manner that at least tames the waves of evil destruction of morality and the strengthening of evil. However, when Hashem will make His nation prominent in the world, they will also give direction and order to the physical world that was given to the nations of the world and teach them how to use these elements for good and justice. Therefore, "many nations will go to the mountain of Hashem and to the house of the G-d of Yaakov" (based on Yeshaya 2:3) to ask them to "teach His paths so that they will go in His ways" (ibid.). However, even in the time of world shleimut, when things will, for the most part, be properly arranged, it will still be necessary to prevent the bad powers of physicality from removing morality and breaking the staff of justice. This is how Chazal interpret the pasuk referring to the times of Mashiach: "The youngster will die at the age of 100, and the sinner will be cursed at the age of 100" (Yeshaya 65:20), which is talking about the nations of the world (Sanhedrin 91b). About Israel it says: "Death will be swallowed up forever and Hashem will wipe tears from all faces" (Yeshaya 25:8).