1)
Why did He say "Lehatzilecha"?
1.
Radak: He did not promise that they will not strike him. They will strike him, and want to kill him, but Hashem will save him. When they came to kill him and Baruch, "va'Yastirem Hashem" (36:26).
2.
Malbim: You said that the nation will rise against you to kill you. I will save you!
