In all of Tanach, the command, "lech lecha (you shall go)" is found only twice, both in regard to our first patriarch. The first time, Hashem told Avram to leave his homeland for the Promised Land, with the promise of success in his future (Bereishit 12: 1-2). The second time is when He commanded Avraham (his name had already been changed) to go to the Land of Moriah and bring his son as a human sacrifice (ibid. 22: 1-2). If we examine the wording of the Torah sections, we will see how strongly the Torah links them. Both refer to the place involved with the root, "to see," whether to be seen or to show. They also use similar language regarding the blessing and reward that Avram was to receive. However, the difference between the promises of blessing is very telling, as we shall demonstrate.
The phrase, "lech lecha," especially its second word, can be explained in two different ways. It can be a manner of speech, to stress the subject of the command, that it is Avram who is to go, even though it is otherwise clear that Avram is the subject (Ramban to 12:1). However, Chazal (brought by Rashi, ad loc.) interpret the word as, for your benefit. Indeed, as promised, Avraham received all that he was promised. He became wealthy and famous. He was the object of the respect and admiration of his time’s world leaders and decided the outcome of the first known world war. He even merited the birth of his beloved son, Yitzchak, born to his formerly barren wife, Sarah.
The background of the second "lech lecha" was very different. After attaining the tremendous success he did and upon approaching old age, Avraham was challenged by a command that would throw everything into jeopardy. He was told to sacrifice his beloved son. What would that make of his attainments? Was he to kill the one so dear to him? To whom would he pass on his legacy? What would the world that so respected him say about a man who went and slaughtered his own son? In this case, there were no promises in advance, just a command to go and bind Yitzchak to the altar. "Lech lecha" couldn’t possibly be for his benefit, one would think.
Actually, Avraham’s willingness to heed the second call demonstrates how he related to the first one. He was prepared to go, just go, without any known benefit, even at the price of losing everything. Indeed he related to the first "lech lecha" the same way. He went to follow Hashem’s command, with any benefits being secondary, at most. Both times, the benefits came. The benefits of the trip to Moriah were revealed only after Avraham had passed the great, moral test. He went thinking like the Ramban, and returned with the understanding of Rashi. And along the way to Moriah, he discovered for future generations where it is that Jews would go to bring up sacrifices and thereby be elevated.