The first Pasuk of Lech Lecha seems fairly straightforward: “VaYomer Hashem El Avram, ‘Lech Lecha MeiArtzecha UMiMoladtecha UMiBeit Avicha El HaAretz Asher Ar’eca,’” “God said to Avram, ‘Go from your land, from your birthplace, and from your father’s house to the land I will show you” (BeReishit 12:1). God tells Avram to travel from his homeland to an unnamed place, which turns out to be the Land of Canaan.
But there is one problem: Where is Avram’s homeland? At the end of Parashat Noach, Avram’s father Terach took Avram on a trip from Ur Casdim to Canaan, but they stopped in Charan for unknown reasons (ibid. 11:31). Was Avram born in Ur Casdim, as the Pesukim imply? If he was, why does God tell him while he is presumably in Charan to leave his birthplace? After all, didn’t Avram already leave his birthplace with his father?
Rashi (12:1 s.v. MeiArtzecha) presents a simple answer: Avram was born in Ur Casdim, but when God spoke to him in Charan, God was merely commanding Avram to distance himself farther from his homeland by journeying to Canaan.
Ibn Ezra (ibid. s.v. Lech Lecha) is bothered that Rashi’s explanation does not fit perfectly with the words of the Pasuk—the words “Lech Lecha MeiArtzecha UMiMoladtecha” imply that Avram was living in his land of birth when God gave him this command. Ibn Ezra instead theorizes that Avram was born in Ur Casdim and received the command to move to Canaan when he was still living there. According to Ibn Ezra, the Pasuk about Terach and Avram moving from Ur Casdim to Canaan but settling in Charan is written out of order, as Avram and Terach only left Ur Casdim after God commanded Avram to do so.
Ramban (12:1 s.v. MeiArtzecha UMiMoladtecha), however, takes issue with Ibn Ezra’s approach as well. First, writes Ramban, if Avram and Terach only journeyed out of Ur Casdim because Hashem commanded Avram to do so, the Torah should have written something along the lines of “Avram left Ur Casdim to go to Canaan, and Terach tagged along,” as opposed to the actual language of the Torah, “Terach took Avram, and they left Ur Casdim to go to Canaan” (cf. 11:31). The latter formulation implies that Terach was the impetus for the trip, not God’s command to Avram.
Second, a Pasuk in Sefer Yehoshua states “BeEiver HaNahar Yashvu Avoteichem MeiOlam—Terach Avi Avraham,” “In Eiver HaNahar (literally “beyond the river”), your ancestors—Terach, the father of Avraham—always lived” (Yehoshua 24:2). According to Ramban, the phrase “Eiver HaNahar” proves that Avraham’s ancestral land was not Ur Casdim, as Ibn Ezra argued, because if it was Ur Casdim, Yehoshua would have said “Your ancestors always lived in Ur Casdim.” According to Ramban, Avraham was actually born in Eiver HaNahar. Through the juxtaposition of several Pesukim elsewhere in Sefer BeReishit , Ramban deciphers that Eiver HaNahar refers to Charan in the land of Aram, over 500 miles northwest of Ur Casdim. Therefore, Ramban concludes, Avram’s birthplace is Charan, and he is in Charan when God commands him to leave for Canaan.
But if Avram’s homeland is Charan, why does Terach take him from Ur Casdim to Charan in the end of Parashat Noach? Shouldn’t Terach and Avram have already been in Charan, their ancestral homeland?
Ramban answers that Avram and his brother Nachor were born in Charan, Terach’s homeland, but then Terach and Avram moved to Ur in the land of Casdim, where Terach fathered Avraham’s younger brother Haran . The rest of the story follows the widely-known Midrash (BeReishit Rabbah 38:13): One day in Casdim, Avram smashes all of Terach’s idols, and in response, Terach brings Avram before the monarch of Casdim, King Nimrod. When Avram remains unrepentant, Nimrod decrees that he be thrown into a fiery furnace . But God performs a miracle and Avram is saved. Upon seeing the awe-inspiring salvation of his older brother, Haran declares himself to be with Avram. He too is thrown into the furnace, but he is devoured by the flames.
The Midrash ends there, but Ramban (11:28 s.v. Al Penei Terach Aviv BeEretz Moladeto) continues the story: Terach and Avram, consumed with grief for Haran and fearing the wrath of King Nimrod, decide to leave Casdim and journey to Canaan, where they will be safe from Nimrod because the language of Casdim, Aramaic, is not spoken there. However, upon reaching his homeland of Charan, halfway to Canaan, Terach stops. Though Aramaic is spoken in Charan, Terach loses the will to complete his goal. He never makes it to Canaan.
It is at this point that Avram is commanded by God to finish the mission he and his father began: to leave his homeland and venture forth into the land of the unknown.
It is fascinating that the first of our ancestors to enter the Holy Land was nearly the idolatrous Terach! We know that Lech Lecha is included in the Asarah Nisyonot, the Ten Tests, that Avraham Avinu was tested with (Mishna Avot 5:3). If Terach nearly travelled to Canaan, why is it considered such a challenge for Avram to do so? What special difficulty does this task have to merit its inclusion in Avram’s Ten Tests?
I believe the answer lies in the details. Terach almost made it to Israel, but he was seduced by the familiarity of Charan and chose to stop. Avram, on the other hand, overcame the “easy way out” to complete the mission of travelling to the Holy Land.
This Ramban teaches us a valuable lesson. The greatness of Avraham Avinu is not that he began to accomplish the tasks assigned to him; the greatness of Avraham is that he never did anything halfway. Once he commenced a task, he would always complete it, regardless of how much more difficult it became along the way. May we be blessed with the grit and perseverance to complete all tasks we begin, as Avraham Avinu did before us.
 In Shmuel Bet 10:17, the phrase “Eiver HaNahar,” “beyond the river,” is used to describe the land of Aram. In BeReishit 24:10, Avraham’s servant travels to the city of Nachor, which is in the land of Aram. In BeReishit 29:4-5, Yaakov Avinu travels to Charan and finds the family of Nachor. Thus, Eiver HaNahar = Aram = city of Nachor = Charan.
 It is unclear what motivated Terach to move to Casdim.
 “Ur” means “fire” in Hebrew. According to Rambam, “Ur Casdim” refers to the furnace into which Avram was thrown, not necessarily the name of a city.
 Many of Avraham’s Ten Tests follow this pattern: they seem relatively easy at first but turn out to be much more difficult than expected. For example, Avram is told to live in Canaan, but then a famine strikes. He descends to Egypt to buy food, but then his wife is taken. Each test becomes harder along the way. His greatness is that he persists and passes the tests despite the increasing challenges.