The opening verse of our parasha is opaque and difficult to understand. The commentators have trouble with the factual assertion that "My Name Y-H-V-H I did not make known to them." A cursory review of Sefer Bereishit shows this not to be true: Avraham is told, "I am Y-H-V-H Who took you out of Ur Kasdim" (Bereishit 15:7), and Yaakov is told, "I am Y-H-V-H, the God of Avraham your father"
Unquestionably, though, the simple meaning of the verse is that God did not reveal the Name Y-H-V-H to the forefathers. As noted above, this clearly contradicts the verses in Sefer Bereishit that tell us that God explicitly told the forefathers, "I am Y-H-V-H."
This article will shed some light on the verse, both locally and in its broader context.
