What did the brothers tell Yaakov that caused him to change his stance and believe them?
Rashi: Yosef told his brothers that the wagons hinted 1 at the last thing that Yaakov had learned with him 2 (the Parshah of Eglah Arufah). 3
Ramban: His sons kept on repeating the words of Yosef, until gradually, he recovered from the shock and "his spirit was revived."
Rashbam #1: When Yaakov heard how Yosef wept on their necks and how they were convinced that he was indeed their brother, he too, believed that it was Yosef, despite the fact that he had seen Yosef's shirt soaked in blood.
Rashbam #2, Hadar Zekenim: When he saw the wagons that Pharaoh had sent, he knew retroactively that Yosef's dream (that he would rule) had come true, 4 for no wagon was allowed to leave Egypt without the king's consent. Da'as Zekenim - Yosef had decreed so.
Seforno: The brothers told Yaakov that there were still five years of famine, thereby balancing the good news. 5
Ha'amek Davar: People do not toil for nothing (Bechoros 29b - and it was a toil to bring wagons! - so what they were saying must have been true.
Riva: This is why the Torah writes here, "the wagons that Yosef had sent," whereas below it says "the wagons that Pharaoh sent" (46:5). (Refer to 45:21:151:1**, refer to 45:21:151:2 and the note there).
Via Torah-study, which proved to his father that Yosef had not dropped his standard in the pervert Egypt, and that he was the same Torah-scholar that had left him twenty-two years earlier. That is what the brothers meant when they told Yaakov (in 45:26) that Yosef ruled over the land of Egypt - It was he who ruled over them, and not they who ruled over him! (EC)
The words 'Eglah' and 'Agalah' share the same letters. See also Ba'al ha'Turim. Moshav Zekenim rejects this. A Siman that others would know is not a good Siman; and presumably, they knew what Yaakov and Yosef were learning! He answers that Yaakov and Yosef learned Eglah Arufah together, only as Yaakov escorted Yosef before sending him. If so, his brothers would not know (Gur Aryeh writes this as well; refer to 45:27:1.1:1).
And this is what enabled him to 'come back to life' when he believed them. Because too much good news in one go can cause a person's death. Note: The Seforno does not actually address the question itself. Refer also to 45:26:1:3*.
What does "va'Techi Ru'ach Yaakov Avihem" mean?
Rashi and Targum Yonasan: The Ru'ach ha'Kodesh that had left him when Yosef disappeared, now returned. 1
Ha'amek Davar: It means that Ya?akov adopted an aura of happiness.
Da'as Zekenim (37:35): When the brothers saw Yosef alive, they permitted the Cherem, and due to this the Shechinah returned to Ya?akov and he believed what the brothers had told him. Hadar Zekenim: Immediately afterwards - in 46:2 - Hashem appeared to Ya?akov. See also Torah Temima, note 13.
The Hadar Zeknim cites Tarfgum Onkelos as?Sharsah Ru?ach Ru?ach ha?Kodesh?, in which case the explanation is close to that of Rashi in answer #1.
Which, the Ramban explains, is Onkelos' interpretation of the word "Ru'ach;" and he adds 'Nevu?ah' because that is what happened. See Ramban, who cites a number of examples of this - one of them in Pinchas, 27:18.
Why does it say, "Kol Divrei Yosef Asher Diber"?
Ha'amek Davar: They elaborated that they will come to Egypt; true matters are recognized.
Rashi said that the wagons hinted to Eglah Arufah. 'Eglah' and 'Agalah' are not the same! Eglah is an animal, and wagons are of wood! If he did not give cattle to pull the wagons, it is not a good Siman!
Rosh: A calf that pulled a wagon is Pasul for Eglah Arufah, so it is a good Siman. 1
Riva (to 45:28): Normally, calves pull wagons. 2
Da'as Zekenim, Hadar Zekenim: Yaakov and Yosef were learning about the wagons used for transporting the Mishkan.
Above, it says, "va'Yiten Lahem Yosef Agalos Al Pi Pharaoh" (45:21), whereas below it says, "Asher Shalach Pharaoh" (46:5). Why does it say here "ha'Agalos Asher Shalach Yosef"?
Ha'amek Davar: Refer to 46:5:151:2.
QUESTIONS ON RASHI
Rashi writes: "Yosef's words' - He gave them a sign; what was he learning when he left? The section of Eglah Arufah." How did it come about that Yaakov and Yosef were learning specifically that topic?
Gur Aryeh: When Yaakov escorted Yosef to Emek Chevron (37:14), Yosef encouraged his father to turn back home, and not exert himself. Yaakov explained that it is a Mitzvah to escort a traveler. Failure to do so is tantamount to murder; whereas the merit of escorting him can protect him from all harm. 1 We derive this from the Parshah of Eglah Arufah (see Sotah 45b).
Maharal (Nesivos Olam, Nesiv Gemilus Chasadim beg. Ch. 5, p. 163): Why is this so? The inhabited areas of the world were given to man, but uninhabited areas are where Mazikim (demons) have control. Accompanying a traveler means he has not left from the domain of the rest of humanity. Furthermore, to escort him shows honor to his Tzelem Elokim, and it is due to a person's Tzelem Elokim that the Mazikim have no power over him.
Rashi writes: "He gave them a sign... he was learning the section of Eglah Arufah." What message was Yosef sending Yaakov with this sign?
Rashi: Yosef hinted to Yaakov that surely he was still alive, for Yaakov had escorted him upon his departure, and anyone who is escorted will not be harmed. Refer to 45:27:1.1:1.
Rashi writes: "This is what [the continuation of the verse] says; 'He saw the Agalos.'" Why did Yosef leave this as a vague hint; he could have asked the brothers to remind Yaakov outright about Eglah Arufah?
Gur Aryeh: Yosef was sending this message via his brothers. Had he told them outright about Eglah Arufah, it would imply that he considered them murderers, and that were it not for Yaakov's escort he would have been killed; and his brothers would feel hurt. Yosef therefore said merely, "These hint to what we last learned together;" and they were none the wiser. 1
Mizrachi: Yosef explicitly told his brothers to tell Yaakov that they last learned about Eglah Arufah. "Saw" means "heard."
