In this week's parashah, 250 people joined with Korach in the machlokes. They said the entire nation is holy, and they can all be kohanim gedolim. They claimed that there was no need for just one kohen gadol. Moshe told them to bring ketores in firepans – Korach, Aharon, and the 250 people (see 16:16). If it is as they desire, Hashem will accept their ketores and they can all be kohanim gedolim. But if Hashem chooses only one person to be the kohen gadol, all the others will die.
The Torah tells us that Moshe became very upset at this machlokes, as it states (16:15) מ ְאֹד ֶׁהלְמֹש וַיִּחַר, and Moshe davened, וַיֹּאמֶר מ ִנְחָתָם אֶל תֵּפֶן אַל 'ה אֶל, "Don't accept their offering".
Some Rishonim explain that מ ִנְחָתָם refers to their tefillah (see Ramban).
The 250 people were praying that Hashem accept their ketores and allow them all to be kohanim gedolim. Moshe davened that Hashem shouldn't accept their tefillos. It seems that Moshe's tefillah was necessary. Otherwise, there was a possibility that Hashem would accept their tefillos.
Ketores and the Power of Prayer
Rashi writes, אליהם תפן אל מחר לפניך מקריבין שהם הקטורת ,פשוטו לפי, "According to its simple meaning [Moshe davened] that Hashem shouldn't accept the ketores that they would bring the following day."
Moshe Rabbeinu told Aharon that he should stop the mageifah with ketores, as it states (17:11) הַמַּחְתָּה אֶת קַח ה ַנָּגֶף הֵחֵל 'ה מ ִלִּפ ְנֵי הַקֶּצֶף יָצָא כִּי עֲל ֵיהֶם וְכַפ ֵּר הָעֵדָה אֶל מְהֵרָה וְהוֹלֵ ךְ ק ְטֹרֶת וְשִׂים ַהַמ ִּזְבֵּח מֵעַל ׁאֵש עָל ֶיהָ וְתֶן, "Moshe said to Aharon, "Take the pan and put fire from the mizbeiach onto it and place the ketores. Then take it quickly to the congregation and atone for them, for the wrath has gone forth from Hashem; the plague has begun." Rashi writes that Moshe learned this secret from malach hamaves (angel of death) when Moshe was in heaven: Ketores stops a mageifah.
The Zohar (Midrash HaNelam, Vayeira p.100) adds that saying the ketores stops all bad decrees and mageifos. "Reb Pinchas taught, 'Once, I was walking on the way, and I met Eliyahu HaNavi. Eliyahu HaNavi told him that when there is a mageifah, Hashem proclaims to all the heavenly hosts that if Bnei Yisrael gather in the batei midrashim and say the ketores with kavanah, the mageifah will end."
The Zohar (vol.2 218) states that saying the ketores with kavanah saves a person from all the bad things in the world, and from all evil thoughts, and "he won't be damaged the entire day, because the Sitra Achara has no power over him."
The Ibn Ezra writes, .יבין והמשכיל ,הקטרת אמר ולא .קטרת ושים :הידועה .המחתה את He is noting that המחתה, the pan, is written with a הי at the beginning of the word, but it doesn't state הקטרת, with a 'ה. The Ibn Ezra concludes, יבין והמשכיל, the wise will understand. The Chernobyler Rebbe Shlita says that the Ibn Ezra is alluding to the lesson which we saw in the Zohar. It isn't solely הקטרת, the actual ketores from the Mishkan or Beis HaMikdash, that can stop a plague. Even when one recites the ketores today, it has the potential to annul harsh decrees and to halt a mageifah.
It states (17:13) הַמ ַּגֵּפָה וַתֵּעָצַר הַח ַיִּים וּב ֵין הַמֵּת ִים בֵּין וַיַּע ֲמֹד, "He stood between the dead and the living, and the plague ceased." Targum Yonason writes, בִּצְלוֹי אַה ֲרן לֵיהּ וְקָם, that Aharon stood in prayer. Why was prayer necessary? He had the ketores, and the ketores had the power to stop the mageifah! Instead, Moshe told Aharon that in addition to offering the actual ketores, he should "say" the ketores. This was to set a precedent for the future generations, when there is no ketores, that they can "say" the ketores, and this, too, has the power to stop a mageifah.
With this information, we can explain the Rashi on this pasuk: "[Aharon] grabbed onto the malach and caused him to stand up, against his will [and to stop the mageifah]. The malach said, 'Let me do my shlichus.' Aharon replied, 'Moshe told me to stop you.' The malach didn't believe that Moshe said he should stop. So, Aharon brought the malach to Hakadosh Baruch Hu and Moshe, who were at the entrance of Ohel Moed, as it states, משה אל אהרן וישב. Only then did the malach stop the plague.
Now, this malach was the malach hamaves, the angel of death, the one who divulged to Moshe the secret powers of the ketores. So why did he argue over whether he must stop the plague or not? When he saw the ketores, he should have understood that his mission was over! He was the one who taught this segulah! But the answer is that the malach taught the segulah of bringing the ketores. But now Aharon was davening and saying the ketores. The malach never said that this, too, would stop the mageifah. This was a new chidush that the malach hamaves wasn't aware of. Aharon brought the malach hamaves to Moshe, so Moshe could tell the malach that saying the ketores also stops a mageifah.
