Why does the Torah interrupt here in the middle of the episode of Yosef and his brothers?
Rashbam: Because it provides us with an additional reason as to why they hated him. 1
As is evident from the next Pasuk.
What is the meaning of "Ben Zekunim hu Lo"?
Rashi #1: It means that he was born to him in his old age. 1
Rashi #2 and Targum Yonasan: "Zekunim" is the acronym of 'Ziv Ikunim' - because Yosef was the spitting image of Yakov.
Rashi #3 (citing Targum Onkelos): He was his wise son 2 - because he taught him everything that he learned in the Yeshivah of Shem and Eiver.
Ramban, Malbim: It was customary for old men to pick one of their younger children to serve them and to lean on - and he was called a 'ben Zekunim'.
Rashbam: Yakov favored him because he was the last of the eleven sons to be born - Binyamin was born much later.
Hadar Zekenim: Even though Binyamin was born later, Yakov did not love him as much, for Rachel died through his birth. Alternatively, Binyamin was too young (nine), and one does not love a young son so much. Also Yakov saw with Ru'ach ha'Kodesh that when Yakov is old, Yosef will be king.
What exactly does "Kesones Pasim" mean?
Rashi #1: It means 'a cloak of fine wool. 1 '
Rashi #2 (in Shabbos 10b), Da'as Zekenim: It is the part of a cloak that covered the hand 2 and that was made of fine wool.
Ramban (Shemos 28:2): An embroidered, striped cloak.
Rashbam: A long coat.
Targum Yonasan: A colored cloak.
Rashi #3: Pasim is the acronym of 'Potifar, Sochraim, Yishma'elim, Midyanim', who bought him (though not in that order), due to the [envy that came due to the] robe. 3
Oznayim la'Torah: It hints at Keri'as Yam-Suf. 4
Ha'Emek Davar: It reached until Pas Yado (his palm).
Why did Yakov make the special robe for Yosef?
Rashi, Ramban, Targum Onkelos and Targum Yonasan: Refer to 37:3:2:1-4.
Oznayim la'Torah (citing Midrash Rabah): He did it as a sign that the Yam-Suf would split on the merit of Yosef. 2
Malbim: The other brothers were always in the field with the flock; they dressed like shepherds. Yosef served Yakov in the house, and needed honorable clothes for his father's honor, like Esav had [special] clothes to serve his father.
Seforno: We find this concept in Bava Kama, 11b.
Ma'aseh Avos Siman l'Banim' - "Pasim" = 'Pas Yam (a path in the sea). Oznayim la'Torah: Because any decree issued by Hashem cannot be withdrawn if one makes a sign to accompany it (See Oznayim la'Torah who elaborates), which explains why Yakov made the cloak in spite of the brothers' inevitable jealousy. (If one can make his own sign, without Hashem's instruction, why was Yakov worried lest sin nullify Hashem's promises (refer to 32:8:4:1)? He should have made a sign! And he could have made a sign without arousing jealousy, e.g. he could tell Yosef not to wear it in front of them, or give to him a torn robe!- PF)
Why did Yakov not make the special robe for Binyamin, who was born when Yakov was even older?
Rosh: Precisely because he was too small to keep it clean.
How could Yakov not take into account the brothers' reaction to his display of favoritism?
The Gemara in Shabbos 10b does indeed comment that Yakov erred in this point - A father should never display favoritism to one son over another. And it concludes that, for two Sela'im of fine wool - the Kesones Pasim that Yakov made for Yosef over and above his brothers - they became jealous of him and, after one thing led to another, our fathers ended up going down to Egypt. 1
Rosh, Moshav Zekenim: Even though exile was already decreed at the Bris Bein ha'Besarim, if not for the special robe, it would have entailed merely going from one land to another - like strangers. (How would this fulfill "va'Avadum v'Inu Osam" (Bereishis 15:13)? Perhaps this would have been pardoned, or fulfilled for a very short time. Hashem said that the servitude and affliction will last 400 years, and it was much less! - PF) Refer to 37:1:4:1***, 2
. See also Oznayim la'Torah DH 'V'asah lo Kesones Pasim'.
The previous verses said "Yakov". Why does this verse say "Yisrael"? The next verse says that his brothers saw that he loved him "mi'Kol Echav." Why does this verse say "mi'Kol Banav"?
Ha'Emek Davar: His love for Yosef was not due to physical matters and service. Rather, there were spiritual reasons to love him. Yakov loved him "mi'Kol Banav", for his nature resembled Yakov more than the others. 1
Presumably, his brothers did not realize this, therefore it says that they saw (assumed) that he loves him "mi'Kol Echav." (PF)