Sefer Ach Pri Tevuah explains this pasuk by saying that it is well-known that all of the mazalos (astrological constellations) are in opposition to Klal Yisroel. Furthermore, according to the natural astrological signs, Klal Yisroel should not exist at all. All of the Avos were barren, and could not have children according to the laws of nature. Therefore, the Jewish nation should never have naturally existed. But Hashem “robbed” (m’shaded) the astrological signs for the sake of the Jewish people.
The reason they merited having nature changed for them was because they “robbed” their own bodies and natural tendencies for the sake of Hashem. This is as Chazal say (Avos 2:4) that if one annuls his natural desires for the sake of others, others will annul their desires for him.
Accordingly, Hashem told Moshe that He appeared to the Avos with the name of Keil Sha-dai, which symbolizes how He robbed (m’shaded) the Heavens for them. But they did not know the name of “Havaya”, which symbolizes His great kindness, as He only did kindness to them in return for the kindness they had done for Him.
Sefer Be’er Mayim Chaim (Parshas Beshalach) writes that Hashem only performs supernatural miracles for people who serve Him in a supernatural way. This is as Chazal say (Sotah 8:2) that a person is dealt with in the way that he acts. This is why Chazal say (Shemos Rabbah 21:10) say that the sea did not split until the Jews entered it up to their noses. The Gemara adds (Sotah 37A) that either Shevet Binyomin or Nachshon ben Aminadav jumped in. Before they risked their lives in a supernatural way, Hashem could not perform supernatural miracles for them.
