Descent from Aaron
Torah text: Stated in the Five Books of Moses.A is a male descendant of Aaron, Moses' brother, in the male line. The rest of the tribe of Levi, the Levites, were joined to the priests to assist them.
כהנים
A is a male descendant of Aaron, Moses' brother, in the male line. The rest of the tribe of Levi, the Levites, were joined to the priests to assist them.
Lineage mattered, and so did the body: priests with certain physical blemishes did not perform the altar service, though they kept their priestly status, gifts and share in the offerings.
The Mishnah describes the Great Sanhedrin sitting in the Chamber of Hewn Stone to examine priests. One found unfit dressed in black and left; one found fit dressed in white and went in to serve.
The priests were divided into twenty-four , each serving in turn. Each watch was paired with a : priests and Levites went up to Jerusalem, and the Israelites of that watch gathered in their own towns and read the story of creation.
So the whole people took part in the service, even from home.
Priests served only in their garments: four for every priest, eight for the Kohen Gadol. The Torah calls them garments ‘for splendour and for beauty’.
Clearing the altar, arranging the wood, the offerings, the incense, tending the Menorah, the showbread, blowing the silver trumpets. Tasks were given by lottery each morning so that no one was denied a share and no one could claim one by force.
After the morning service the priests stood on the steps of the Sanctuary and blessed the people. In the Temple they said God's Name as written and raised their hands above their heads.
יְבָרֶכְךָ ה׳ וְיִשְׁמְרֶךָ׃ יָאֵר ה׳ פָּנָיו אֵלֶיךָ וִיחֻנֶּךָּ׃ יִשָּׂא ה׳ פָּנָיו אֵלֶיךָ וְיָשֵׂם לְךָ שָׁלוֹם׃
The LORD bless thee, and keep thee; The LORD make His face to shine upon thee, and be gracious unto thee; The LORD lift up His countenance upon thee, and give thee peace.
Priests had to be ritually pure to serve and to eat holy food. Contact with the dead is the most severe impurity in the Torah, and priests avoid it except for close relatives. Purity is a matter of ritual status, not of hygiene or moral worth.
Many Jewish families still hold a family tradition that they are kohanim, often with surnames like Cohen, Katz or Kahane. They are called first to the Torah, bless the congregation in synagogue, redeem firstborn sons and avoid contact with the dead.
There is no Temple service today. Whether and how priestly lineage would be established for a future Temple is discussed by authorities; the site does not take a side.