Sarah laughed when she heard the malachim say she would bear a child, and Hashem rebuked her for laughing. The Ramban (18:15) explains, "Hakadosh Baruch Hu explained to Avraham what Sarah did wrong. Why does she think it is impossible [for her to bear children]? She should believe, or she should say, 'ה יעשה כן אמן, 'Amen, may Hashem do so.'" But why did she laugh? Why did she think it was impossible?
The Chofetz Chaim zt'l (Kisvei Chofetz Chaim) explains that this is a significant story for us because there will be a time when we will be told that Moshiach is about to come. Some people will laugh. They will say that it can't be. This parashah teaches them that we must believe in the upcoming salvation and we must believe in miracles.
The Imrei Noam (Dzikov) zt'l teaches, "Hakadosh Baruch Hu performs miracles for tzaddikim, and He leads them above the rules of nature. This is because the tzaddik believes in Hashem's hashgachah pratis even when the world is run according to the rules of nature. So there is no reason to conceal from him."
The explanation is as follows: Hashem leads the world according to the rules of nature. This is because if Hashem's presence were evident, there would be no test for a man to believe in Hashem. Hashem hides behind the guise of nature to enable free choice to exist. However, a tzaddik believes in Hashem even when His ways are concealed. Therefore, Hashem has no reason to conceal Himself from this tzaddik. For the tzaddik, the guise has been unveiled, so there is no reason for concealment. This is the reason miracles occur to tzaddikim. Therefore, it states (18:17) אני המכסה אמר 'וה עושה אני אשר מאברהם, "And Hashem said, 'Shall I conceal from Avraham what I am doing?'" Hashem was saying, "Why should I conceal matters from Avraham? Avraham knows that it is Me, concealed behind the guise of nature, so there is no purpose in hiding. And therefore, Avraham can enjoy open miracles, too."
Chazal say, בניסו מכיר הנס בעל אין. Literally, this means that when Hashem performs a miracle for someone, the person generally doesn’t realize it. He thinks that he was saved through natural means. Hashem performs great miracles for him, and he doesn't even know it.
The Kedushas Levi (Beshalach, 15:11) explains the words בניסו מכיר הנס בעל אין in another way. He explains that these words are counsel on how to merit miracles. He says that a miracle should be as wondrous to him as nature because they are both Hashem's doing. To explain, let us read the Kedushas Levi's words:
"When a person needs a miracle from His Creator, he should think that this isn't a miracle; rather, Hashem can do anything. Small and large matters are the same for Him. If he has this emunah and bitachon in Hashem when he needs something, he will receive it regardless of what it is. He will be helped from heaven. The condition is בעל אין בניסו מכיר הנס, which can mean that he can't recognize that it is a miracle. He shouldn't consider it a miracle or a change in nature; rather, it is according to the rules of nature that Hakadosh Baruch Hu performs miracles. When a person is wise and has understanding, he knows that just as Hashem can make oil give forth light, Hashem can also say that vinegar should bring light (see Taanis 25.) or whether the sea should be stormy or calm. Miracles are easy for Hashem yisbarach. Hashem doesn't need extra effort to perform a miracle."
When a person believes that nature is also part of Hashem's wonders, miracles and nature are one and the same. The only difference is that nature is more common, but they are both the performance of Hashem yisbarach. The wonders are equal. The Kedushas Levi explains that when a person has this emunah, he merits seeing miracles. It states in Az Yashir (Shemos 15:11) פלא עשה, "performing wonders!" The Kedushas Levi explains that the wonder isn't so much the miracle itself because that is easy for Hashem to do, and that is the same wonder as every other aspect of creation. The wonder is that Hashem is in heaven, so exalted above us, yet He loves and cares for the Jewish nation. Hashem's love to us, His hashgachah pratis on us, is the wonder!
The Kedushas Levi explains, "Every day, the sea, with its waters, flowed forcefully, and on this day [of kriyas Yam Suf], the sea split. This proves that Hashem loves Yisrael... Hashem's wonder is that He is in the upper worlds and loves physical human beings."
