“And this is the thing that thou shalt do unto them to hallow them, to minister unto Me.”
– Exodus 29:1, JPS 1917 Tanach
During Moshe’s forty days on Mount Sinai, the pattern of the Mishkan (Tabernacle) was shown to him, complete with all the details necessary to construct a Mishkan on earth, where H’Shem’s Presence – the Shechinah – would dwell. Also, the commandments and details in regard to the Kohein Gadol (High Priest), and the kohein (priests) were given.
Aaron was chosen as the first Kohein Gadol; however, Moshe served unofficially in that position, during the seven-day inauguration, when he brought the offerings. His role was given to him by H’Shem, who said to Moses: “This is the thing [word] that thou shalt do to them [the kohein] to set them apart as kodesh [holy];” i.e., to sanctify them for service to H’Shem.
The verse continues with the offerings, necessary for the inauguration. Also, the commandment is given for the kohein to cleanse themselves in a mikveh. Also mentioned are the garments that Moses will place upon the Kohein Gadol, before anointing him with oil. These garments, referred to previously, are described as “holy garments for Aaron thy brother, for splendour and glory” (Exodus 28:2, JPS).
“Let Thy priests [kohanim] be clothed with righteousness” (Psalm 132:9, JPS 1917 Tanach ). Righteousness is likened to clothes, because righteous thought, speech, and acts clothe the soul; they have everlasting value, whereby our righteousness will be rewarded in Olam Haba.