What is the significance of the words "ba'Yom ha'Hu, Leimor"?
Ramban: The Torah is pointing out that on the very same occasion, not only did Yaakov refuse to remove his right hand from the head of Efrayim, but he went on to mention Efrayim before Menasheh.
Ohr ha'Chayim: He gave to them so many Berachos, that there is no greater Berachah. Everyone said that so it is proper to bless Yisrael.
Malbim: Efrayim's Berachah 1 came first that day, for it already applied (the potential for the future greatness was already in Efrayim's Nefesh), unlike Menasheh's Berachah (quantitative increase), which did not exist that day.
Ha'amek Davar: It teaches that this is not a continuation of the previous Berachah, which applied to Yehoshua and Gid'on, when they led their generations. The current Berachah is for Efrayim and Menasheh themselves. (Whenever Yisrael will bless, they will say....)
Why is the word "Leimor" spelled with a 'Vav'?
Ba'al ha'Turim #1: Because in six places, the Torah places Efrayim before Menasheh. 1
Ba'al ha'Turim #2: To hint at the six righteous Shoftim that would descend from him.
Tosfos ha'Shalem (5): This hints at six Berachos (each Berachah of Birkas Kohanim (Bamidbar 6:24-26) is two, e.g. "Yevarechecha" and "v'Yishmerecha").
See Ba'al ha'Turim.
Seeing as Yaakov is speaking about Efrayim and Menasheh, why did he say "Becha" in the singular?
Ramban: Although Yaakov is speaking about Efrayim and Menasheh, he is actually telling Yosef that Yisrael will bless their sons through his (Yosef's sons). 1
Moshav Zekenim: Yaakov meant that a man will bless and say to his son "[Bnei] Yisrael will bless through you."
Bearing in mind that, the fact that they were worthy of taking his place as two tribes, was a tribute to him, for having succeeded in bringing them up in the midst of Tum'as Mitzrayim.
What did Yaakov mean when he said, "In you Yisrael will bless ... "?
Rashi, Rashbam and Targum Yonasan: He meant that whenever a Yisrael comes to bless his son, 1 he will bless him with the words of this Pasuk, "Yesimecha Elokim ... "
Ha'amek Davar: It does not say Bnei Yisrael, for it does not discuss the entire nation; rather, people of a high level, fitting to be called Yisrael.
According to Targum, it speaks specifically on the day of his son's Bris.
Why does the Torah need to state that Yaakov put Efrayim before Menasheh?
Rashi: To teach us that Efrayim would precede Menasheh with regard to the Degalim in the desert (Bamidbar 2:18,20), and by the inauguration of the Nesi'im (in Bamidbar 7:48,54). 1
Ramban: It means that he placed Efrayim before Menasheh in all his Berachos.
Targum Yonasan: It means that when listing the tribes, Efrayim takes precedence over Menasheh.
Ohr ha'Chayim: Via this, he fixed Efrayim before Menasheh, for who in Yisrael would change from the order of Yaakov, and bless his son to be like Menasheh and Efrayim!? This shows that Efrayim is before Menasheh for everything.
Ha'amek Davar: We already know that Efrayim is first for spiritual matters, and Menasheh for worldly matters. However, who should be first in name? Perhaps it should be Menasheh, for 'Derech Eretz Kadmah l'Torah' - we find that Zevulun (who worked to enable Yisachar to learn) is mentioned before Yisachar! 2 Yaakov taught that Efrayim is first - Kevod Torah precedes authority. Zevulun is different, for he enabled Yisachar's Torah. 'Shimon Achi Azaryah' was called on his brother's name, for his brother caused his greatness in Torah (Rashi to Zevachim 2a). Also, one who supports Torah is elevated somewhat like one who engages in Torah - he merits to sit in the Heavenly Yeshivah (Pesachim 53b).
See Ba'al ha'Turim (DH 'Efrayim').
In Yaakov's blessings (49:13-14); as well as Moshe's (Devarim 33:18).
Why will they bless to be specifically like Efrayim and Menasheh? Yaakov had other blessed grandsons, e.g. Peretz and Zerach!
Ha'amek Davar: Efrayim and Menasheh each had a greatness different than the other. Efrayim was great in Torah and clung to his G-d; whereas Menasheh in ways of the world and engaging in needs of Yisrael. 1
Chidushei ha'Griz (Hosafos, Vayechi): The other Shevatim reached their levels because they were raised (a) via Yaakov, and (b) in Eretz Yisrael. Efrayim and Menasheh lacked both of these. Even so, they reached the level of the Shevatim, and were not influenced by the surrounding Tum'ah of Egypt!
Harchev Davar: Targum Yonasan says that they will bless so at the time of Bris Milah. It is proper to bless someone only according to what Hashem blessed him until now - an Ashir with his wealth, a Chacham with his Chochmah. If so, if one does not engage in Torah, how can we bless him to be like Efrayim? If one does not engage in worldly matters, how can we bless him to be like Menasheh? At the time of Milah, it is not yet known what path the boy will take. We bless, if he will engage in Torah, he should succeed like Efrayim. If he will engage in worldly matters, he should succeed like Menasheh.
QUESTIONS ON RASHI
Rashi writes: "Yisrael shall bless through you - [I.e.,] one who wishes to bless his sons, will invoke their blessing...." What is Rashi clarifying?
Gur Aryeh: This is not to be taken as a positive Mitzvah (i.e. that one must bless one's sons using this formula). Yaakov did not have the prerogative of commanding Mitzvos upon his descendants! 1 Rather, this was a blessing that Menasheh and Efrayim would become so important, that people (of their own accord) would use them as a blessing.
Compare to 2:24:0.1:1.
Rashi writes: "He placed Efrayim [before Menasheh] - in his blessing." Why does the Torah highlight this only now? Yaakov already used this order in 48:5!
Gur Aryeh: Refer to 48:5:152.1:1 and 48:5:152.1:2.
