Why does it say "va'A'as Lema'an Shmi"?
Malbim: Even though they deserve eradication, I was concerned for the honor of My name, lest it be profaned.
What is the meaning of "l'Vilti Hechel"?
Rashi: My name should not be profaned 1 . Since I was known to them, and promised to take them out, and Egypt recognized that they are My nation, if I would destroy them, their enemies would say that it was due to His inability to take them out.
Radak: The Tzeirei under the Ches is in place of a Patach. Also "Ki Sechel Liznos" (Vayikra 21:9) is profaning.
How did He become known to them?
Radak: It was via the Nevi'im.
Why does it say "l'Eineihem"?
Radak: The Egyptians heard the Nevi'im speak to [Yisrael], and promised to take them out even before Moshe. When Moshe came to them on Hashem's mission, they did not persist in their evil deeds - "va'Ya'amen ha'Am va'Yishme'u Ki Fakad Hashem Es Bnei Yisrael" (Shemos 4:31). They believed in Moshe due to the signs that he did in front of their eyes; the first Nevi'im did not do so.
