"I used to appear to Abraham..." (Ex. 6:3)

G‑d's relationship with each one of the patriarchs was based on something unique to the patriarchs in question.

The reason G‑d did not lump the three patriarchs together but referred to each one by name is that G‑d's relationship with each one of the patriarchs was based on something unique to the patriarchs in question. Abraham was unique in that he recognized his Creator without having had guidance from another human being.

If someone had foreknowledge of the existence of G‑d and His power, he does not deserve special credit for conducting himself in line with such knowledge. Every intelligent being would choose good over evil once he possessed such knowledge. Abraham did not possess any of these advantages which would have acquainted him with G‑d's attributes. The reason G‑d called Abraham "the one who loves Me" (Isaiah 41:9) was because his faith and morality was the result of his being a "self-starter." He cleaved to his faith in G‑d in spite of the most demanding tests G‑d subjected him to.

Isaac possessed another unique characteristic; he had submitted without question to his father's request made in the name of G‑d to give his life for that G‑d. He did not even ask for an explanation of why he had to give his life.

Jacob was unique in not wasting a single drop of semen by producing offspring which was not worthy of him. All his children remained loyal to his teachings.

G‑d explained to Moses that He had not revealed His attribute of the four-lettered name Y-H-V-H which He had revealed to Moses to any of these three patriarchs, but had revealed to them only His attribute Shaddai. G‑d now told Moses that in view of the revelations He had already made to him, he had displayed ingratitude by speaking to Him in an inappropriate, critical manner.

Abraham remained unaware of the difference between G‑d in His capacity as El Shaddai and G‑d in his capacity as Y-K-V-K.

While it is true that in the Torah's report of G‑d's communications with Abraham (Gen. 18:1) we find such an expression as "vayeira HaShem el Avraham" (Y-K-V-K appeared to Abraham), which seems to suggest that G‑d revealed this aspect of His attributes to Abraham, this is misleading. G‑d may have dealt with him on that basis, but He had not confided that fact to Abraham, i.e. Abraham remained unaware of the difference between G‑d in His capacity as El Shaddai and G‑d in his capacity as Y-K-V-K. This is what G‑d meant when he said "they were not informed of My name Y-K-V-K."

G‑d also meant that the patriarchs were not aware of the unique simultaneous effectiveness of both of G‑d's attributes, as we mentioned in connection with verse two. The mystical dimension of this is recorded when the assembled people realized this after Eliyahu's demonstration on Mount Carmel. (Kings I 18:39)

…There may be yet another nuance in G‑d's saying "I have appeared to Abraham." The implied message is G‑d's rhetorical question: "How could I turn a deaf ear to a nation who is the offspring of My most beloved Patriarchs, to each of whom I made a point of revealing Myself separately at the appropriate time?" The Torah made a point of not writing Abraham, Isaac, Jacob, but of interposing the word 'to' each time. This underlines that each one of the patriarchs merited a revelation in his own right. In spite of all this, G‑d continues, I still did not reveal the aspect of the attribute of Mercy to these patriarchs. One of the reasons I could not do this was because I had not yet demonstrated how this Mercy is expressed in practice, such as now when I am about to change My timetable for the redemption.

[From "Ohr Hachayim" by Rabbi Chayim ben Attar, translated and annotated by Eliyahu Munk, Vol. I]