Yaakov prepares for his descent to Egypt, bidding a final farewell to the Land of Israel. Along the way he stops in Beer Sheva:
And Yisrael journeyed with all that was his, and he came to Beer Sheva; and he offered sacrifices to the G-d of his father Yitzchak (Bereishit 46:1).

The usual route to Egypt is the coastal road, “the way of the land of the Philistines” (Shemot 13:17). When Yitzchak had intended to travel to Egypt, he passed through Gerar (Bereishit 26:1). (Gerar is identified with either Tell Yamma, Tell al-Shari’a or Tell Hurayra, all west of Beer Sheva.)

Beer Sheva, on the other hand, is a detour on the way to Egypt. Situated on the southern border of the territory of Yehudah, Beer Sheva is on the edge of the desert; it is more likely a stop on the way to Chorev (see Melachim I 19:3, 8) than to Egypt.

This, explains Maharzu (R. Zeev Wolf Einhorn), is the meaning of the question in the Midrash (Bereishit Rabba 94:4):
“Where did he go?”
Why does Yaakov take the indirect route to Egypt via Beer Sheva?

We first encounter Beer Sheva (the well of oath) as the location of a well dug by Avraham when he entered into a non-aggression treaty there with Avimelech, who acknowledged Avraham’s water rights (Bereishit 21:25-32). Later, this was one of the wells that the Philistines stopped up; it was rediscovered and renamed by Yitzchak (26:25, 32-33; see Ramban). Yaakov too left from his home in Beer Sheva before going to live with Lavan (Bereishit 28:10).

Beer Sheva also has spiritual significance for the Patriarchs. After the destruction of Sodom, Avraham sought another place to do acts of chesed (Bereishit Rabba 52a), and he came to Beer Sheva:
And he planted an eshel in Beer Sheva and there he called upon the Name of Hashem, G-d of the world (21:33).

Yitzchak moved ever farther from Gerar:
And he ascended from there to Beer Sheva. And Hashem appeared to him that night and He said, “I am the G-d of Avraham your father. Do not fear, for I am with you. I will bless you and increase your seed because of Avraham My servant.” And he built there an altar and called upon the Name of Hashem (26:23-25).

Yitzchak had been told not to venture out of the Land of Israel (26:2). Therefore, says Sforno (R. Ovadia ben Yaakov Sforno, c. 1470-c.1550), as Yaakov now prepares to do what his father was forbidden, he hesitates;
and he offered sacrifices to the G-d of his father Yitzchak (46:1)
to obtain Hashem’s assurance, which he receives (46: 2-4).

Rashbam says Yaakov now offers sacrifices in Beer Sheva because Yitzchak had built an altar and offered sacrifices there (26:25). Ramban observes that Beer Sheva was a place of prayer for the Patriarchs. Yaakov himself had received Hashem’s permission to leave from there for Charan.

The Midrash cited above (Bereishit Rabba 94:4) answers:
“Said R. Nachman, ‘He went to cut down cedars that his ancestor Avraham planted in Beer Sheva, as is said, And he planted an eshel, etc.’”
Yaakov takes Avraham’s trees to Egypt, and these will provide the shittim wood for building the Mishkan.

Emet LeYaakov (R. Yaakov Kamenetsky,1896-1981) here and on 26:23-25 elaborates on Sforno, Rashbam and Ramban: When Avraham planted trees there, Beer Sheva became sanctified as
“a source of consolation for the Patriarchs that in the future they would leave the exile and build the Mishkan.”

Therefore after he was exiled by Avimelech, Yitzchak went to Beer Sheva and built an altar there. He took comfort in Hashem’s promise that his exile would not last.

This is Yaakov’s intention now:
“Likewise Yaakov before entering the exile went to Beer Sheva in order to draw consolation that the children of Israel would indeed leave Egypt. Therefore he offered sacrifices to the G-d of his father Yitzchak.”

Yaakov fears lest his descendants become so immersed in Egyptian values that they would not want to leave (as in fact nearly occurred):
“Because of this fear Yaakov wanted to make a real connection between his offspring that are descending to Egypt and the land of Israel. Therefore he insisted that these trees always be with them. The idea was passed from generation to generation as the tradition of our patriarch Yaakov: ‘Do you not see that the time of redemption will certainly come? For here are the trees that our ancestor Yaakov brought from the Land of Israel, and they are the very ones that our ancestor Avraham our patriarch planted in Beer Sheva, and they stand ready for us to build the Mishkan with them when we leave Egypt. Therefore it is certain that we will leave here soon!’ By means of these trees they encouraged one another until the time of the redemption actually arrived.”

This is similar to Megillah 31b, where Avraham asks Hashem, what shall his children do if they sin so as to prevent them from being lost? Hashem answers that the offering of sacrifices will atone for them. Avraham exclaims:
“That is well during the time when the Temple is standing; but when the Temple is not standing, what will become of them?”
He said to him, “I have already established the order of sacrifices for them. Whenever they read them I consider it for them as if they were offering a sacrifice before Me, and I forgive them for all their sins.”

R. Kamenetsky explains Avraham’s concern:
“As long as the Temple stands and the Divine Presence is in its glory and Israel are on their land, I am certain that they will not be lost, because they are connected with an everlasting bond to their land and their people. However, when the Temple is not standing and they are in exile, dispersed and disjoined among all the nations, what will become of them? How will they preserve the connection to their source and the hope for redemption?”
Hashem’s answer is that as long as they learn about the sacrifices they will remain connected to the belief in the coming of Mashiach.

As our Patriarchs taught us, the way to redemption is our desire to be redeemed.