Why did Moshe instruct Aharon to stop the plague by means of the Ketores?
Rashi (on Pasuk 13): To demonstrate that the Ketores can stop plagues too, because it is not the Ketores that causes plagues but sins. 1
Rashbam: To demonstrate that the same Ketores that kills those who are not Kohanim, gives life when it is in the hands of Kohanim
Rashi: To counter the people's claims that the Ketores is poison
How did Moshe know that the Ketores stops plagues?
Rashi: When Moshe ascended Har Sinai, the Mal'ach ha'Maves taught him the secret that the Ketores stops plagues. 1
See Shabbos, 89b
What is the significance of the term "Ketzef" that the Torah uses here?