not just a matter of perspective

The gemara (B.M. 86) writes that when Avraham saw that he had no guests, he sent Eliezer out to look for some, but Eliezer came back emptyhanded.  “There is no trust in slaves,” said Avraham, and he went and sat by the doorway to look for himself.  We know the rest of the story – Avraham sees the three angels approaching, etc. 

Did Avraham think Eliezer was not telling the truth, or was being lazy?  On Parshas Noach I quoted the Oheiv Yisrael who teaches that emunah transforms reality – if one believes things will work out, then they will.  Avraham was not saying that he did not trust Eliezer.  What he was saying is that Eliezer lacks the same level of trust, of bitachon, that he, Avraham, has.  Therefore, although Eliezer went looking for guests, he failed to find what he was looking for.  Avraham had greater faith in the mitzvah, and so when he went looking, he found what he wanted (Sifsei Tzadik). 
 
Two people can experience the same situation and one will be filled with hope while the other sees only gloom.  Eliezer saw an empty desert; Avraham saw angels walking by.  It's not just a psychological trick.  The reality changes according to the amount of bitachon invested.

Before we get to the arrival of the angels, Avraham was busy “entertaining” G-d himself – “Vayeira eilav Hashem...” Rashbam learns al pi peshuto that these are not two episodes, but one: the appearance of G-d to Avraham was manifest through the arrival of the angels.  Rashi, Ramban, Seforno, and Chazal interpret these as separate ideas.  Chazal learn that Avraham turned away from interacting with G-d and concerned himself with his guests, proving that the mitzvah of hachnasas orchim is even greater than interacting with the Shechina.  (How can that be?  R’ Naftali Ropshitz quoted in Imrei Shefer cleverly reads the letter “mem” in the statement “gedolah hachnasas orchim M’kabalas pnei haShechina” not as “greater than,” but as “from.”  From the experience of giluy Shechina Avraham grew in his hislahavus to do more mitzvos, to do more hachnasas orchim. See Netziv for a hesber with less twist.)  The Torah doesn’t tell us why Hashem appeared and doesn’t tell us anything that was said to Avraham during this encounter.  Rashi writes that nothing needed to be said; Hashem came to do bikur cholim and just being there was enough.  Seforno explains that Hashem appeared in response to Avraham’s having done bris milah.  Bris means covenant, and you can’t make a covenant without both parties being present.  Hashem therefore appeared to seal the agreement.  In Parshas Shmos where we read that Moshe arrived at an inn and, “vayifgasheihu Hashem,” it does not mean, as  Rashi there tells us, that an angel came to punish Moshe, but rather G-d was appearing to ratify the bris that would be made when Moshe circumcised his son.  This is why, adds Seforno, we set out an extra chair whenever a baby enters the covenant of bris milah – we are welcoming the presence of the Shechina as our partner in the bris.  A fantastic makor for the minhag of Klal Yisrael.

What perhaps motivated the Seforno’s comment, or at least implicit in his comment, is an answer to the Mizrachi’s question.  Why are Rashi and other mefoshim convinced that “Vayeira eilav Hashem…” should be connected with the previous parsha of milah?  Maybe, asks Mizrachi, it is connected with the upcoming parsha, where Hashem informs Avraham that he will be destroying Sdom?  Given Chazal’s interpretation that Avraham’s meeting with Hashem was interrupted by the arrival of the angelic guests, maybe what happened is that Hashem appeared and was about to start that conversation about Sdom, but Avraham broke off the engagement and began serving his guests.  Once he was done, Hashem picked up where they left off. 

The answer in one word, according to Seforno, is bris.  It takes two to tango.  Hashem’s appearance must be connected with milah because a bris demands that both parties be engaged.  Since there is no record on the previous parsha of Hashem doing anything in response to the bris, this must be it.

Ramban (and Gur Aryeh suggests this as well) suggests a different answer based on a simple rule of grammar: a pronoun always needs an antecedent.  You can’t say, “He went to the store” without first telling me who the “he” you are talking about is.  If the sentence, “Vayeira eilav Hashem,” is meant as the start of a new topic, then the antecedent for “eilav” is missing -- it should say, “Vayeira Hashem el Avraham.”  The sentence makes sense only because we know who “eilav” is because we read it as a continuation of the previous parsha.

All this is background/warmup to the Midrash’s take on the parsha that will tie everything together:

ואחר עורי נקפו זאת ומבשרי אחזה אלוה
אמר אברהם: אחר שמלתי עצמי, הרבה גרים באו להדבק בזאת הברית.
ומבשרי אחזה אלוה, אילולי שעשיתי כן, מהיכן היה הקדוש ברוך הוא נגלה עלי?!
וירא אליו ה'.

Avraham said, “If not for my bris milah, how would Hashem have appeared to me?”  Again, we see Chazal connecting “vayeira…” to the previous parsha by way of cause and effect: Avraham did a milah, therefore, G-d can now reveal himself.  If you remember the beginning of last week's parsha you will be scratching you head over this.  We read last week, “Vayeira Hashem el Avram…” (12:7).  Hashem did appear to Avra[ha]m long before he had a bris milah.  “Vayeira” is not a chiddush due to the bris, but is old news.   

The Sefas Emes answers that there is a big difference between “vayeira” before milah and the “vayeira” after milah. The “vayeira” before the milah is “vayeirah HASHEM el Avraham” – Hashem is the actor, the subject who is the focus of the sentence, the one who intercedes and appears in Avraham’s life.  Ramban gives a long list of similar places where Hashem appears on the scene to bless Bnei Yisrael (Vayikra 9:23) or to stop a rebellion (Bamidbar 14:10).  If we were staging these events as a play, the spotlight would shift to kavyachol a new character, G-d, stepping onto the stage.  The “vayeira” after the milah inverts things.  “Vayeirah EILAV Hashem” – the focus is Avraham himself, the same character we’ve been talking about until now.  The text focuses our attention on the point grammatically by using a pronoun whose antecedent is in last weeks’ parsha -- the spotlight doesn’t shift; no one new steps onto the stage; it’s the same cast as last week.  So what changes?  It’s Avraham’s perception that changes.  Hashem’s presence, which last week had been invisible to Avraham the not-yet-nimol, is suddenly visible to him everywhere. It is not G-d stepping onto the stage that is the chiddush here; it's Avraham perceiving G-d who was already there beforehand. 
 
So we've come full circle.  Just like Avraham can see angels where Eliezer sees an empty desert, Avraham after the bris can now see, “vayeira eilav,” and the world is very different than it looked before.