1. "And Hashem said to Moses, Speak to the priests the sons of Aaron, and say to them, There shall none be defiled for the dead among his people" (Vayikra 21:1). Rabbi Yosi said, What is the reason that this corresponds with that which is said before, "A man also or woman that is a medium or a wizard, shall surely be put to death" (Vayikra 20:27), so that THE VERSE, "Speak to the priests" is adjacent to it? HE REPLIES: Once admonishing Yisrael to sanctify themselves in every manner, it also admonished the priests to sanctify themselves and the Levites as well. How do we know it admonished the priests? From the words, "Speak to the priests." And as for the Levites, it says, "Thus speak to the Levites, and say to them" (Bemidbar 18:26). Thus they will all be righteous, holy and pure.
2. "Speak to the priests the sons of Aaron:" HE ASKS, What is the reason it is written here, "the sons of Aaron?" Do I not know they are the sons of Aaron? AND HE ANSWERS, THIS TEACHES US they are "the sons of Aaron" rather than 'the sons of Levi,' because Aaron is the first of all the priests. For it is him that the Holy One, blessed be He, had chosen above everyone, so as to make peace in the world, and because Aaron's practices have brought him up to this. For Aaron strove throughout his life to increase peace in the world. Since these were his ways, the Holy One, blessed be He, raised him TO PRIESTHOOD, to introduce peace among the celestial retinue, FOR THROUGH HIS WORSHIP HE BRINGS ABOUT THE UNION OF THE HOLY ONE, BLESSED BE HE AND HIS SHECHINAH, WHICH BRINGS PEACE THROUGHOUT THE WORLDS. Hence, "Speak to the priests the sons of Aaron."
3. "Speak to the priests the sons of Aaron, and say to them." Rabbi Yehuda opened with the verse, "O how great is Your goodness, which You have laid up for those who fear You..." (Tehilim 31:20). "O how great is Your goodness:" how superior and precious is that lofty light that is called good, as it is written, "And Elohim saw the light, that it was good" (Beresheet 1:4). This is the treasured light with which the Holy One, blessed be He, does good in the world. He does not withhold it any day, and the world is maintained and supported by it. "Which You have laid up for those who fear You:" for we have learned that the Holy One, blessed be He, made a lofty light when He created the world, and treasured it for the righteous for the future to come. This is the meaning of, "which You have laid up for those who fear You, which You have performed for those who trust in You."
4. "Performed for those who trust in You" (Ibid.): for when the world was created, this light was shining from the beginning of the world to its end. When the Holy One, blessed be He, saw the wicked that will live in the world, He concealed that light. This is the meaning of, "And from the wicked their light is withheld" (Iyov 38:15). THE HOLY ONE, BLESSED BE HE, will shine it upon the righteous in the World to Come, so, "which You have laid up for those who fear You, WHICH YOU HAVE PERFORMED FOR THOSE WHO TRUST IN YOU." "PERFORMED" ALLUDES TO THE ACTION OF CONCEALMENT. It is also written, "But to you who fear My name the sun of righteousness shall arise with healing in its wings" (Malachi 3:20).