Ramban

AND BEHOLD A LADDER SET UP ON THE EARTH AND THE TOP OF IT REACHED TO HEAVEN; AND BEHOLD THE ANGELS OF G-D ASCENDING AND DESCENDING ON IT. In a prophetic dream, He showed Jacob that whatever is done on earth is effected by means of the angels, and everything is by decree given to them by the Supreme One. The angels of G-d, whom the Eternal hath sent to walk to and fro through the earth, would not do anything minor or major until they return to present themselves before the Master of the whole earth, saying before Him, “We have traversed the earth,, Verse 11. and behold it dwells in peace, or is steeped in war and blood,” and He commands them to return, to descend to the earth and fulfill His charge. And He further showed him [Jacob] that He, blessed be He, stands above the ladder, and promises Jacob with supreme assurance to inform him that he will not be under the power of the angels, but he will be G-d’s portion, and that He will be with him always, as He said, And, behold, I am with thee, and will keep thee wherever thou goest for his [Jacob’s] excellence is superior to that of the other righteous ones of whom it is said, For He will give His angels charge over thee, to keep thee in all thy ways. And in the opinion of Rabbi Eliezer the Great this vision was akin to the one seen by Abram at the time of the covenant “between the parts” for He also showed Jacob the dominion of the Four Kingdoms,. Jacob, like Abraham, was thus shown the events that will happen to his descendants during all the generations of their exiles. their ascent and descent. This is the meaning of angels of G-d (mentioned here), just as it is said in the visions of Daniel: the prince of the kingdom of Greece, and the prince of the kingdom of Persia., Verse 13. Similarly, the angels mentioned in the verse before us are to be understood as the representatives of the various nations. And He promised him that He, exalted be He, will be with him wherever he will go among the nations, and He will guard him and rescue him from them. Thus the Rabbis have said: “The Holy One, blessed be He, showed him the Four Kingdoms, their dominion and their destruction. He showed him the prince of the kingdom of Babylon ascending seventy rungs and then descending the ladder. Then He showed him the prince of the kingdom of Media ascending one hundred and eighty rungs and then descending. And then He showed him the prince of the kingdom of Edom ascending and not coming down. Jacob then said to the prince of Edom, Yet thou shalt be brought down to the nether-world. The Holy One, blessed be He, said to [the prince of Edom], Though thou make thy nest as high as the eagle, etc.”.