Genesis 15:12

And when the sun was nearing to set, a deep sleep was thrown upon Abram: and, behold, four kingdoms arose to enslave his children: Terror, which is Bavel; Darkness, which is Madai; Greatness, which is Javan; Decline, which is Pheras, which is to fall, and to have no uplifting, and from whence it is to be that the children of Israel will come up.

AND LO, A DREAD, EVEN A GREAT DARKNESS FELL UPON HIM. The Rabbis in the Midrash have interpreted this fourfold expression to be an allusion to the servitude of the four exiles, for the prophet Abraham found his soul overtaken by “a dread,” followed by “darkness,” which in turn became “a great darkness,” and then he felt as if an overwhelmingly heavy load “fell” upon him. Thus the Rabbis have said: “A dread, this is Babylon. Darkness, this is Media that darkened the eyes of Israel with fasting and affliction. Great, this is the kingdom of Antiochus. Fell upon him, this is Edom.
This experience came to Abraham because when the Holy One, blessed be He, made a covenant with him to give the land to his children as an everlasting possession, He said to him, by way of a residuary of His gift, that during the four exiles the nations will subjugate his children and rule in their land, subject to the condition that they sin before Him. Following this general allusion, He then informed him explicitly concerning another exile into which they will first go, namely, the Egyptian exile with which he had already been punished, as I have explained.

ויהי השמש לבא, this verse proves that this whole paragraph describes a prophetic vision, that the entire sequence is a continuous vision, uninterrupted. Both the story about G’d taking Avraham out of his tent to gaze at the stars (did not have to have occurred at night) and the time frame mentioned here, i.e. the sun setting, did not have to refer to 12 hours having elapsed since the earlier reported part of this vision. The Torah reports matters in the sequence in which they appeared to Avram in the vision. The reason why “evening” “night” and, by implication, the preceding “daylight” is mentioned, is because they symbolise periods in Jewish history. Daylight symbolises when the fortune smiled on the Jewish people, whereas “sunset” symbolises the decline of the fortunes of the Jewish people, and “night, darkness” symbolises the periods during which the Jewish people are in exile. The approaching evening mentioned in our verse refers to the first Jewish exile in Egypt.

ותרדמה נפלה על אברם, this exhaustion was due to the marshalling of all of Avram’s spiritual resources to receive these prophetic visions. We have evidence of these reactions in Daniel 8,18 who describes these physically debilitating reactions when he involuntarily went to sleep on the very ground on which he had been standing. (he did not have time to lie down on a bed) He had to be revived by the angel. He referred to such weakness also in verse 17 of that same chapter. Avram, at least at the beginning of his prophetic vision, did not experience such a weakness. The reason was that at the beginning of the visions G’d showed him there were only positive developments. Now when G’d showed him the downside, he was overcome with the impact of what G’d showed him.

אימה חשכה, as if the Torah had written אימה וחשכה, fear and darkness. We have similar constructions where the conjunctive letter ו is simply omitted in Chabakuk 3,11 שמש ירח, and in Exodus 1,2 ראובן שמעון, and many others like it.

ותרדמה נפלה על אברם, “and a deep darkness (sleep) had fallen upon Avraham. During this sleep G–d showed Avraham that his descendants would endure the enslavement to several kingdoms at different times as well as the collapse of these kingdoms (empires). When he was told to קחה לי עגלה משולשת, “take for Me a three year old calf,” (verses 8) this was a reference to the fourth (and last) of these empires, which would subjugate the Jews more cruelly and for longer than any other. This has been confirmed by a vision experienced by Daniel, (Daniel 7,7) with the words: דחילה ואמתני, “excessively terrifying and awesome.” The עז משולשת , “three year old goat,” represents the Greek empire. (Daniel, 8,5 וצפיר העזים בא מן המערב, “and the-goat came from the west across the surface of the whole earth.) The three year old ram, איל משולש, represents the empire of the Medes and Persians; mentioned in Daniel 8,8, i.e. וצפיר העזים הגדיל עד מאד, “and the he-goat grew exceedingly.” The תור, in our verse refers to the empire of the Ishmaelites. The word here has to be understood as the aramaic,תר ,שור, “ox or bull”. (The author on a Targum, unfamiliar to this editor) The גוזל in our verse refers to the Jewish people. It appears in that sense in Song of Songs, 2,14, as well as in the same Book, 6,9).
Rabbi Acha claims that the word משולש and משולשת is a metaphor for anything that is exceedingly strong. He quotes as support for his view Kohelet 4,12: והחוט המשולש לא במהרה ינתק, “and the threefold cord will not tear easily.” Rabbi Mesharshia, interpreting the word משולשים, understands the rule of the empires while the Israelites are under their domination as occurring during three different periods in history. The first time each of these empires states, or Kingdoms, dominates the Israelites on their own. unaided by other powers. The second time, two of those powers combine in subjugating the Israelites On the third occasion, during the period ushering in the messianic age, they all combine in their assault, as a result of which the Messiah will appear. He quotes Psalms 2,2; יתיצבו מלכי ארץ ורוזנים נוסדו יחד על ה' ועל משיחו, “all the kings of the earth and its regents will take a combined stand against the Lord and His messiah.” Rabbi Yoshua, in referring to the phrase: ויבתר אותם בתוך “he divided them in the middle,” understand the subject in that phrase as being the respective swords of Avraham’s opponents, thus breaking their power in half. He adds that if Avraham had not …