(2) God spoke to Moses and said to him, “I am the יהוה LORD. (3) I appeared to Abraham, Isaac, and Jacob as El Shaddai, but I did not make Myself known to them by My name יהוה LORD.
The Torah made a point of not writing Abraham, Isaac, and Jacob but of interposing the word אל, El, "God of", each time. This underlines that each one of the patriarchs merited a revelation in his own right. In spite of all this, God continues, I still did not reveal the aspect of the attribute of Mercy (יהוה) 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.
(Or HaChaim is Chaim ibn Attar (1696-1743) a Moroccan rabbi who wrote a commentary on the Torah.)
ושמי ה׳ לא נודעתי להם BUT BY MY NAME THE LORD WAS I NOT KNOWN TO THEM — ...I was not recognized by them in My attribute of “keeping faith”, by reason of which My name is called יהוה, which denotes that I am certain to substantiate My promise, for, indeed, I made promises to them but did not fulfill them [during their lifetime].
(Rashi is Rabbi Shlomo Itzhaki (1040-1105) a medieval French Rabbi who is famous for authoring some of the most extensive commentary on Talmud and Tanach.)
...That attribute [אל שדי, El Shaddai] is one which is inflexible. It reflects the fact that God has set absolute limits to certain developments. However, that attribute is part of the overall attribute אלוהים, Elohim, Justice, an attribute which governs God's manifestations in nature. God had not taught Abraham that by appealing to His attribute of רחמים, Rachamim, Mercy, the limitations which are part of the אל שדי El Shaddai syndrome can become more flexible. Since the prayers of the whole Jewish nation had reached His attribute of Mercy this is why He decided to respond before the time which had originally been designated for the redemption. God began by saying that he was י־ה־ו־ה Adonai in order to teach Moses that when one "knocks on the door of Mercy," such knocks are apt to evoke a response on the other side of that door.
I love the idea about "such knocks are apt to evoke a response." It reminds us that if we don't engage with God, we can't develop a relationship with God. We may be upset, frustrated, grateful, happy, whatever emotion when it comes to God, but if we never explore that or acknowledge those feelings, we lose out on an opportunity to engage with God and potentially evoke a response.
This Shabbat, may we take the time to explore our relationship with God, however that may look at that very moment, and allow our knocks to evoke responses.