Why did Yitzchak begin the Berachah with a 'Vav' ("v'Yiten")?
Rashi #1: He blessed Yaakov that HaSh-m should give him, again and again.
Rashi #2: It is a continuation to the previous Pasuk - 'Besides the beautiful aroma that HaSh-m already blessed you, may He also give you from the dew of the Heaven....'
Yerushalmi (Berachos 5:2): The Berachos that HaSh-m bestowed upon Avraham that were established for his descendants ('be'Daytiki') are now being handed down to Yaakov 1 (and not to Esav).
Ohr ha'Chayim #1: In addition to the higher world that Avraham chose for his children, which is the primary purpose of spiritual Berachos, HaSh-m will also give [Berachah] to you in this world.
Ohr ha'Chayim #2: "V'Yiten Lecha ha'E-lokim" - also Midas ha'Din should agree [that you receive these Berachos].
See Torah Temimah, who explains the Derashah.
Why did Yitzchak bless Yaakov, "E-lokim will give to you," whereas in the similar Berachah to Esav, he did not mention E-lokim?
Rashi: "E-lokim" denotes Midas ha'Din - implying that Yaakov 1 will only merit the Berachos if he deserves them. Whereas to Esav he said "'mi'Shemanei ha'Aretz Yihyeh Moshavecha" (27:39) - whether he deserves it or not. 2
Teshuvos Beis ha'Levi, Derush 3 DH uv'Zeh, from the Zohar: Only Yaakov receives directly from HaSh-m.
Ohr ha'Chayim: Refer to 27:28:1:5.
Ha'amek Davar: This was like Noach's Berachah to Yefes. Nochrim know only the name E-lokim.
Even though he thought that he was blessing Esav, he was unware of the fact that Esav was not worthy of the Berachos, and that his words, therefore, were directed at the one who was in fact worthy.
Rashi: Shlomo ha'Melech in Melachim I, Chapter 8, took his cue from Yitzchak, and applied the same distinction to a Jew and a Nochri who would pray in the Beis-ha'Mikdash. The reason for this is because, as opposed to a Jew, who understands that if his prayer is not accepted, it is because he is not worthy, a Nochri thinks that since he took the trouble to pray to HaSh-m, HaSh-m is obligated to respond favorably. So if, for some reason or other He doesn't, he turns his back on Him.
What is the gist of the Berachah that Yitzchak was giving Yaakov? What is the significance of the "dew of the Heaven and the fat of the earth"?
Rashi and Targum Onkelos: He blessed him literally with the dew of the Heaven....
Targum Yonasan: He blessed him with 'the best of the dews from the Heaven, from the best of the underground springs and bountiful plants of the earth....'
Ramban #1: That HaSh-m should give him from the dew of the Heaven and the fat of the earth - more than the norm. 1
Ramban #2: That He should give him from the dew of the Heaven and the fat of the earth, an abundance of grain and wine. 2
Ramban #3: Bearing in mind that what HaSh-m gives is forever, he blessed him that HaSh-m should give him from the dew of the Heaven forever, and that his land should be the most fruitful in the world. 3
Ramban (citing the Ibn Ezra): That He should give him from the dew of the Heaven and from the fat of the earth. 4
Malbim: He gave to him three matters of wealth and possessions, and Berachos of authority and honor. The former are dew of Heaven, the fat of the earth, and much grain and wine.
Since 'from the dew of the Heaven and the fat of the earth' is not a Berachah per se, as that is a natural occurrence that happens everywhere.
As if there was no 'Vav' at the beginning of the word "v'Rov."
Because the 'Mem' from "mi'Tal" extends to "Mish'manei..." (so that it reads "mi'Mishmanei ha'Aretz").
Why did Yitzchak mention "mi'Tal ha'Shamayim" before "mi'Shemanei ha'Aretz" when he blessed Yaakov, but reverse the order when he blessed Esav (27:39)?
Oznayim la'Torah: Because when, he blessed Yaakov (thinking it was Esav whom he believed to be a Tzadik), he intended him to receive the Berachos only when he turns his eyes heavenwards and prays. Hence he began with 'Tal ha'Shamayim,' since his Berachah comes, first and foremost, from the Heaven and only then from the earth; But when he subsequently blessed Esav, whom he had discovered was a Rasha, 1 he began with 'Shemanei ha'Aretz,' which he will receive whether he prays or not, 2 and HaSh-m will bless his bountiful land. 3
Why did Yitzchak add, "v'Rov Dagan v'Sirosh"?
Ramban: Refer to 27:28:3:4.
Seforno: He blessed him that he should have sufficient to feed others. 1
Why is "v'Sirosh" written without a 'Vav' (as if it was punctuated with a 'Kamatz'), but pronounced with a Cholam?
Yoma 76b: If Yisrael merit it, they will be on top ('Rosh' with a 'Vav'); if they don't, they will be impoverished ('Rash').
Why did Yitzchak not bless Yaakov with children?
Oznayim la'Torah: Because, although he considered Esav to be a Tzadik, knowing that his Chiti wives worshipped idols and caused him and Rivkah much bitterness, he did not wish him to have children who would not go in the ways of HaSh-m. 1
Oznayim la'Torah: And he reserved that Berachah for Yaakov, later in the Parshah - see 28:2.
QUESTIONS ON RASHI
Rashi writes: "'And may He give to you' (v'Yiten Lecha) - May He give, and give again!" How is this implied?
Mizrachi: Even without the conjunctive "and," the verse would mean that the same blessing should be granted again and again [no limitation on the blessing is stated]. The verse means that HaSh-m should give these Berachos, and then give Avraham's Berachos as well.
Gur Aryeh: Yaakov was given a blessing without boundaries or limits; any blessing granted to Yaakov would lead to even more. This is indeed derived from the extra Vav, which does not connect to the previous verse.
Rashi writes: "'From the dew of the heavens' - There are many homiletic Midrashim." Why does Rashi point this out?
Gur Aryeh: We might be surprised at the brevity of these blessings, and their focus on food and the physical. Rashi therefore references the Midrashim, which expound the blessings in terms of the spiritual as well. Yitzchak had all of the interpretations in mind.