This week’s Parsha opens with the Pasuk, ויאמר ה' אל אברם לך לך מארצך וממולדתך ומבית אביך אל הארץ אשר אראך, “Hashem said to Avram, ‘Go for yourself from your land, from your relatives, and from your father’s house to the land that I will show you.’” Rashi comments on the words לך לך that it was להנאתך ולטובתך, “for his benefit.” Rashi then comments on the words אשר אראך that Hashem did not tell Avram where he was going in order to make it precious in Avram’s eyes and give it to Avram as a reward.
Rav Yaakov Kaniefsky (the Steipler), in Birchat Peretz, learns from the second statement of Rashi that if
Hashem had immediately told Avram to which land he was going, he would not have received all of the reward. The Steipler explains that had Avram been aware of what was coming to him, his fulfillment of Hashem’s command would not have been totally for the sake of Heaven; his own desire to receive a reward would have interfered with his desire to serve Hashem. Since Avram did not know which land he was to receive, his travels were based totally on faith in Hashem and not on his own desires. His travels were for the sole purpose of fulfilling Hashem’s command and therefore he was able to receive his full reward.
A similar idea is seen in various other Sefarim. Based on Rashi’s comment on the phrase לך לך, Avram knew that he was going to receive a reward for his fulfillment of Hashem’s command. The test of Avram was not whether he would leave his home, but whether he would do it for himself or for Hashem. Based on 12:4, it appears that Avram passed the test, as the Pasuk states: וילך אברם כאשר דבר אליו ה'. Avram fulfilled the commandment not for his own benefit, but because he was commanded to do so by Hashem.