Génesis 15:16 Midrash: Midrash Tanchuma, Seder Olam Rabbah, Mekhilta DeRabbi Yishmael & Bereshit Rabbah

God led them not by the way of the Philistines (ibid. 13:17). He guided them in the manner indicated in the verse Thou didst lead Thy people like a flock (Ps. 77:21), and as in the verse By day also He led them by a cloud (ibid. 78:14). By the way of the land of the Philistines, although that was near. The word near indicates that the promise the Holy One, blessed be He, had made to Abraham was soon to be fulfilled. Near also implies that it was the nearest way to return to Egypt. Furthermore near relates to the oath Abraham had sworn with Abimelech. Now therefore, swear unto me here by God, that thou wilt not deal falsely with me, or with my son, nor with my son’s son (Gen. 21:23) was near fulfillment, even though his grandson had not yet been born. Furthermore, near implies that the previous war was too recent to risk another.¹The “previous war” being the one referred to in the continuation of the verse: lest … the people repent when they see war (Exod. 17:1). A tradition exists that the descendants of Ephraim left Egypt before the designated time and 300,000 were killed. See Ginzberg, Legends, vol. 3:8–9. Only ten escaped. Another explanation of Although that was near. It was too close to the time in which the Canaanites had obtained the land, for it is written: And in the fourth generation they shall come back hither (ibid. 15:16), and the fourth generation had not yet come. God led the people about by the way of the wilderness (Exod. 12:18). The Holy One, blessed be He, said: If I lead them into the land by the most direct route, they will each take possession of a field and a vineyard and neglect the law. Therefore I will lead them through the wilderness for forty years and cause them to eat the manna and drink the water of the well so that the law may penetrate into their very beings.

From Adam to the Flood was 1656 years, and this is their enumeration: Adam 130, Seth 105, Enosh 90, Kenan 70, Mahalalel 65, Jared 162, Enoch 65, Methuselah 187, Lamech 182, and Noah was six hundred years old, etc." (Genesis 7, 6). Enoch buried Adam, and lived after him 57 years. Methuselah exhausted his days just before the Flood. From the Flood to the division [of languages] was 340 years. Noah lived ten years after the division [of languages]. Our father Abraham was at the division [of languages] 48 years old. Rabbi Yosei said: Eber was so great a prophet that he [preemptively] named his son Peleg ["division"], [aided] by the Holy Spirit. [Eber having foreseen what was to come] as it says "in his days the earth was divided" (Genesis 10, 25).

"by way of the land of the Philistines, for it was near": Near (i.e., "close") is the thing of which the Holy One Blessed be He spoke to Moses (Exodus 2:12): "When you take the people out of Egypt, you will serve G–d on this mountain." Variantly: "for it was near": It afforded easy return to Egypt, viz. (Ibid. 5:3) "Let us go a three days' distance in the desert." Variantly: "for it was near": Close (in time) was the oath that Abraham had sworn to Avimelech, viz. (Genesis 21:23) "And now, swear to me here by G–d that you will not deal with me falsely (by trespassing on my land), or to my son or my grandson," and his grandson was still alive. Variantly: "for it was near": The first war (that with Egypt) was too close to the second (that with Canaan). Variantly: "for it was near": The Canaanites had only recently acquired the land, and (Genesis 15:16) "And they (the Israelites) shall return here in the fourth generation, for the sin of the Amorites is not yet complete."