בא אל פרעה כי אני הכבדתי את לבו ואת לב עבדיו
Rashi explains that Hashem sent Moshe to warn Pharaoh of the upcoming plague. Why warn Pharaoh if his reaction would be negative as a result of Hashem hardening his heart? A warning should serve a purpose. Apparently, this warning did not. Horav Yosef Dov Soloveitzchik, zl, Rosh Yeshivas Brisk, Yerushalayim, explains this based upon a principle quoted from Horav Yeruchem Levovitz, zl, Mashgiach Yeshivas Mir. When Sarah Imeinu gave birth to Yitzchak Avinu at the age of 90 years old, the Torah makes a big “to do” about the overt miracle that she had experienced. In contrast, when Yocheved gave…