The Darchei Mussar explains that there are two types of malachim. The first type was created in the six days of creation, and the other type of malach is created by every mitzva that someone does. Every time that someone does a Mitzva l’shem shamayim, with kavana and an emunah sheleima a strong malach is created, whereas if the Mitzva is not done with these criteria a weak malach is created.
This then makes sense in the conversation between Avraham Avinu and the malach when Avraham was about the sacrifice Yitzchak. The malach says “Now I know that you fear HaShem, don’t sacrifice your son before me” – The obvious questionis asked on this possuk; why did the malach say “Now I know…” and the malach should have said “…before HaShem”. From the above we can say that when the malach says that it knows that Avraham feared HaShem, it is because the malach himself was created through the Mitzva of Akeidas Yitzchak! And how could the malach testify that the Mitzva was done le’shem shamayim with full Kavona? He looked at himself and saw he was strong..
