The opening verse of Parashat Vayera tells that God appeared to Avraham in Elonei Mamrei. Oddly enough, however, we do not find God speaking to Avraham at all at this point. For what purpose, then, did God appear to Avraham?
According to some commentators, the premise of this question, that God did not speak to Avraham at this point, is incorrect. The Rashbam explains that this opening verse, which tells of God's appearance to Avraham, is explained in the parasha's second verse: "He lifted his eyes and saw three men standing near him… " Meaning, God appeared to Avraham through the visit of the three strangers, presumably angels, to Avraham's tent. Rabbenu Yosef Bekhor Shor explains differently, that the appearance to Avraham mentioned in the opening verse is continued later in the parasha, when God informs Avraham of His plans to destroy the city of Sedom (18:17). This appearance is interrupted by the story of the angels' visit, but it is to this conversation that the parasha's opening verse refers.
The Midrash, cited by Rashi, adopts an entirely different approach to explain this appearance of God, claiming that the Almighty came to visit Avraham, who was recovering from his circumcision, which he performed in the previous section (end of Parashat Lekh-Lekha). No instruction, blessing or other form of prophecy is recorded here because God appears to Avraham not to convey any eternal message, but rather on a "personal note," as it were, in fulfillment of the mitzva of "bikur cholim" (visiting the sick).
A different connection between God's appearance to Avraham and the patriarch's circumcision is suggested by Seforno, in his explanation of the purpose behind this divine revelation. Circumcision, as we know, is referred to as a "berit," a covenant established between the individual and God. The establishment of a covenant, by its very nature, requires the presence of both parties involved. Therefore, when Avraham performs his and his household's circumcisions, the Almighty comes to participate, as it were, in this covenantal ceremony. Seforno concludes his commentary to this verse with a fascinating insight, suggesting that this concept underlies the widespread practice of preparing an extra, empty chair at every circumcision ritual. While we generally refer to this chair as "kisei shel Eliyahu," the chair designated for the prophet Eliyahu, Seforno suggests that it is in fact the chair of the Shekhina. God must be present, so-to-speak, at every circumcision, as through this ritual He enters into a personal covenant and relationship with the newborn Jewish child.
Rav Ezra Bick, in his shiur on Parashat Vayera for the VBM parasha series seven years ago, explains that this silent appearance of God signifies a fundamental transformation in Avraham's status effected by his performance of circumcision. The covenant with God represented by circumcision means that Avraham is no longer merely a regular human being with whom God occasionally speaks. Rather, the entire nature of his existence is changed. In Avraham's new position, God can appear to him even without any specific directive or information to convey. Rav Bick writes:
"… in this case, the appearance is its own purpose. After the mila, God visits Avraham to spend time with him, in fellowship, for Avraham now belongs to the society of God and not that of men. Every previous appearance of God to Avraham was to tell him something specific. Here it symbolizes the fellowship of God and Avraham. Mila has changed Avraham's status from that of a righteous individual to that of 'yedid Hashem,' a part of the spiritual community. He is a 'ba'al berit' of Hashem, rather than a 'ba'al berit' of Aner, Eshkol and Mamrei [as he is described earlier – 14:13]."
After Avraham's circumcision, God needs no reason to appear to Avraham. Having joined "the society of God," Avraham has risen to the stature where God appears to him merely "to spend time with him," even without any specific instruction or information to transmit.