1)
What is the meaning of "va'Yomer Lehashmidem"?
1.
Malbim #1: It was decreed to wipe them out.
2.
Malbim #2: If not for Moshe, Hashem would have said (decreed) to wipe them out - "Heref Mimeni v'Ashmidem" (Devarim 9:14). From this, Moshe knew that it depends on him.
2)
Why does it say "Amad ba'Peretz"?
1.
Radak: The breach that they made, Moshe stood in it in front of Hashem, and fenced it.
2.
Malbim: He stood in the breach to turn back Hashem's anger. Even though the plague already began and people died, the Af (external anger) was not mixed with inner anger to destroy.
