Hashem said, "Am I concealing from Avraham what I plan to do? And Avraham will surely be a great and mighty nation, and all the nations of the earth will be blessed through him. For, I have chosen him so that he charge his children and household after him, that they will keep the way of Hashem to do righteousness and justice, so that Hashem may bring upon Avraham all that He spoke."
The Ohr Hachaim explains these pessukim and their underlying meaning. Avraham saw that a third angel had come along, and he was appointed to bring difficult decrees to the world. He saw the first two Mal’achim and recognized their ????; one to heal Avraham and one to bring the good news to Sarah. He still did not know what the third Mal’ach was appointed for. Moreover, when the scene with Avraham was over, he saw two angels making their way to Sedom, but the third disappeared. Obviously, something was afoot, how could Hashem conceal it from His loyal servant? Hashem had to tell it to Avraham before He does anything.
Chazal write that Avraham really meant to argue with Hashem and tell Him that the story of the Mabul was unacceptable. Why did Hashem not allow the zechus of the Tzadikim to protect the world against destruction? This is why the possuk uses a constant tense אשר אני עשה – that which I do. This is referring to the actions Hashem often does. How could Hashem cover up the actions that He does and not explain Himself to Avraham?
Another reason that Hashem had to reveal to Avraham that which He was about to do to Sedom was because Avraham was the one who fought with Kedarla’omer in last week’s Sedra, in order to retrieve Lot and his possessions. If Sedom was anyway to be destroyed, Avraham would have to be notified. Sedom is Avraham’s nation, after he was the one to save them and they are his nation.
The Ohr Hachaim now explains the next possuk. Avraham was going to become a great nation, and Hashem needed to teach the world and Avraham the great Maidrega of Tzadikim that they not only save themselves, they save the entire city. Avraham was destined to be the one to father a great nation, and the entire world will be blessed through him, he will be the Tzadik of the generation, and the zechus of Klal Yisroel was destined to protect the entire world with their greatness. He needed to learn how to daven for others.
Hashem knew that Avraham would teach his children whatever he learned, and they too will act as they should. When they learn from Avraham how to daven for the world, they too will protect the world with their tefillos.
The Ohr Hachaim now explains the end of the possuk. לְמַעַן הָבִיא ה' עַל אַבְרָהָם אֵת אֲשֶׁר דִבֶׁר עָלָיו – so that Hashem may bring upon Avraham that which was promised on him. This tells us that the important character in the story is Avraham, not his children. Hashem wished to being Beracha to Avraham, through blessing his children forever, and that was through their knowledge of His ways.
