“He slaughtered feast-offerings to the God of his father Isaac” – Rabbi Yehoshua ben Levi said: I circulated among all of the aggada experts in the south so that they would explain this verse to me,7His question was why Jacob invoked the God of Isaac and did not mention Abraham. but they could not tell me [the explanation] until I stood with Yehuda ben Pedaya, the son of ben Kappar’s sister. He said to me: ‘If a teacher and disciple are walking on the way, one first inquires after the wellbeing of the disciple, and then one inquires after the wellbeing of the teacher.’8The disciples would walk before the teacher.
That is why Jacob invoked the name of the God of Isaac and not the God of Abraham. Rav Huna said: When Rabbi Yehoshua ben Levi came to Tiberias, he asked Rabbi Yoḥanan and Reish Lakish. Rabbi Yoḥanan said: ‘A person is obligated in the honor of his father more than the honor of his grandfather.’ Reish Lakish said: He sacrificed offerings for the covenant of the tribes.9This is the covenant that God made with Abraham that would be fulfilled through Isaac and not Ishmael (see Genesis 17:21).
Bar Kappara and Rabbi Yosef bar Patros, one said: [Jacob said:] ‘Just as Father was eager to satisfy his throat, I, too, am eager to satisfy my throat.’10Isaac had loved Esau because of the food he brought him (see Genesis 25:28), and Jacob was descending to Egypt to be sustained by Joseph (see Etz Yosef). The other said: [Jacob said:] ‘Just as Father distinguished one son from his other son, so, too, I distinguished one son from my other sons.11Jacob had shown preferential treatment toward Joseph, which had led to the events that brought Jacob to travel to Egypt, and he now brought offerings in order to achieve atonement (Etz Yosef).
Alternatively, in Egypt, Joseph would rule over and provide for the entire family, which would give him an elevated status (Yefeh To’ar). Therefore, Jacob said he was going to Egypt despite this danger only because of the needs of the many people who required sustenance. Then I said: Father had only the burden of one life, but I have the burden of seventy lives upon me.’12Jacob said he was descending to Egypt.
Rabbi Yudan said: [Jacob said:] ‘Father blessed me with five blessings. Corresponding to them, the Holy One blessed be He appeared to me five times and blessed me.’ Rabbi Yudan said another [explanation], Rabbi Yudan said: [Jacob said:] ‘I was under the impression that He would give me a taste of those blessings.’ What were those blessings?
“Peoples will serve you and nations will prostrate themselves to you” (Genesis 27:29) – this is Joseph.13Jacob saw that one of the blessings granted to him by Isaac was being fulfilled through Joseph, so he brought offerings of thanksgiving, and particularly mentioned “the God of his father Isaac.” Rabbi Berekhya said two [statements], Rabbi Berekhya said: The Holy One blessed be He associates His name with a living person only for those who undergo suffering.
That is why it is not written here: “He slaughtered feast-offerings to the God of Jacob,” but rather, “to the God of his father Isaac,” who was already dead. Rabbi Berekhya said another [explanation]: It is because he had undergone suffering. The Rabbis say: Isaac’s ashes are viewed as though they are accumulated upon the altar. That is why he mentioned Isaac.