The Parshah opens with HaSh-m's choice of Avraham, and the promises that He made to him. Ramban asks - The Torah does not tell us why Avraham was chosen?
Ramban: Avraham left Ur Kasdim for Eretz Kena'an, together with his father, because of the persecution that he suffered at the hands of the locals (due to his belief in the One and only G-d), as is hinted at the end of Parshas Noach. 1 Because his father had stopped in Charan, HaSh-m instructed him to move on, to fulfill his original intention of moving to a place where he could freely serve HaSh-m and bring others under the wings of the Shechinah.
Maharal #1 (Derech Chayim 5:17, p. 262): Had a reason been written, we would infer that HaSh-m's choice was conditional; that if Avraham's descendants were to sin, they might lose their chosen status. Now that no reason is written, HaSh-m's love for them is unconditional and permanent. 2
Maharal #2 (Derush l'Shabbos Ha'Gadol, Hagadah Shel Pesach p. 205): In Avraham's day, the Shechinah had returned to the highest Heavens, and HaSh-m's guidance was not apparent in the world. Avraham was puzzled about this. HaSh-m responded that he should separate from the Resha'im in his locale, and go to Eretz Yisrael, the land that HaSh-m Himself watches and supervises. 3
See Targum Yonasan to 11:28.
Maharal (Netzach Yisrael Ch. 11, p. 68) adds that HaSh-m's choice of Avraham included the entire nation of his descendants, independent of the actions or conduct on their part.
This seems to imply that Avraham's selection for this mission was not a reward for his deeds, but rather to provide him a fitting environment in which to serve HaSh-m. (EK)
Why did HaSh-m use the expression "Lech-Lecha" (go for yourself)?
Rashi: What HaSh-m meant is that moving to Eretz Kena'an would be to Avraham's benefit - 'because it is in Eretz Kena'an that a. he would ultimately become a great nation, and b. he would merit to have children. 1 Moreover, there HaSh-m would cause his good name to spread.
Rashi (on Bereishis Rabah): It is in Eretz Kena'an that he will serve HaSh-m, but as long as lives in Chutz la'Aretz it is as if he did not have a G-d.
Ramban #1: It is perfectly normal for the Torah to insert the word "Li," "Lecha" or "Lo" (and he presents a number of examples to that effect).
Ramban (citing the Ibn Ezra 2 ): The Pasuk means that HaSh-m told Abraham to leave his homeland earlier on (while he was still in Ur Kasdim).
Ramban #2 (citing the Midrash): Once from Aram Naharayim (the country where he was born) and once from Aram Nachor (the capital).
Riva, from Bereishis Rabah (and Rosh Hashanah 16b): Change of place can tear up harsh decrees.
Avraham already left his homeland and birthplace (Bereishis 11:31). Why does HaSh-m tell him now to leave them?
Rashi: Granted, he had left Ur Kasdim 1 to go to Charan, but HaSh-m now instructed him to distance himself even further.
Ramban: Avraham was not born in Ur Kasdim, rather in Charan, where he was residing with his father when HaSh-m told him to leave.
Why did HaSh-m see fit to mention Avraham's land, birthplace and family?
Ramban: It is hard to leave one's home country, even harder to leave one's home-town, and harder still, one's family. HaSh-m was testing Avraham here to see whether his love of Him exceeded that of all else that was dear to him.
Why did HaSh-m not simply tell Avraham in advance exactly where to go?
Rashi: To endear Eretz Kena'an in Avraham's eyes (as is the way of secrets), and to reward him for each set of instructions as he fulfilled it. 1
QUESTIONS ON RASHI
Rashi writes: "'Lech Lecha' - for your benefit; for your own good." Why does Rashi use this doubled expression?
Gur Aryeh: If Avraham would receive only one benefit, the verse should specify it. The general statement "Lech Lecha" must mean that there would be numerous benefits.
Rashi writes: "'Lech Lecha' - for your benefit; for your own good."There are other instances, however, when "Lecha" does not mean this?
Gur Aryeh: In other verses, 1 what is implied is "go by your own initiative." Here it cannot mean that, because HaSh-m was commanding Avraham to go.
Rashi writes: "There, I will make you a great nation (12:2), whereas here (in Charan) you will not merit to have children." This contrast is not parallel; it should say, "... here, you will not become a great nation."
Gur Aryeh: The blessing to have children is specifically connected to the merit of living in Eretz Yisrael (Yevamos 64a); also refer to 16:3:3.2.