Parashat Toledot tells of the experiences of Yitzchak, including the two prophecies that he received from God. The first occurs as Yitzchak is forced to relocate due to the harsh drought that gripped the region of Canaan. God appears to Yitzchak and commands him to settle in the Philistine region of Gerar rather than move further south to Egypt (26:2-3). Yitzchak beholds a second prophecy later, after he was driven out of Gerar and struggled with the Pelishtim who contested his rights to the wells he dug. In this prophecy, God reassures Yitzchak and reaffirms the promise that he will produce a great nation (26:24). Yitzchak responds to this prophecy by constructing an altar and “calling in the Name of the Lord” (26:25), giving rise to the question of why he did not react similarly to the initial prophecy he received, when he first headed toward Gerar.
The Meshekh Chokhma suggests that God Himself indicated to Yitzchak in the second prophecy that he should construct an altar. In this prophecy, God promises to make Yitzchak’s descendants numerous “because of My servant Avraham.” The Meshekh Chokhma contends that the term avdi (“My servant”) is intended as an allusion to the avoda, sacrificial rituals, and God sought to emphasize to Yitzchak that his father had offered sacrifices on numerous occasions to express his devotion to God. In this way, God hinted to Yitzchak that he, too, should serve God in this manner, and Yitzchak therefore responded immediately by constructing an altar and offering sacrifices.
The Meshekh Chokhma offers another approach, as well, attributing the difference between Yitzchak’s responses to the difference between the two prophecies. In the first prophecy, God affirmed that Yitzchak’s descendants would inherit the Land of Canaan, whereas in the second, He spoke only that Yitzchak would beget innumerable offspring. The purpose of “calling in the Name of the Lord” at an altar in response to prophecy, the Meshekh Chokhma suggests, is to publicize that prophecy. And for this very reason, he claims, Yitzchak did not “call in the Name of the Lord” after receiving the first prophecy, in which he was promised that his descendants would take possession of Canaan. The Meshekh Chokhma writes:
He did not publicize it because he feared the residents of the land, lest their enmity be aroused against him, and Yitzchak had never waged battle in his life. Additionally, it would not be ethical that the people of the land are peaceful with him and he seeks to possess their land. Therefore, he did not publicize this vision and did not construct an altar.
Either out of fear or the concern for ethical conduct, Yitzchak felt it inappropriate to publicize God’s promise that his descendants would possess the land, and so he did not construct a religious site after receiving the first prophecy. The second prophecy, however, made no mention of this promise, and Yitzchak therefore constructed an altar where he publicized the prophecy he received.