Exodus 40:15

15 Anoint them as you did their father, so they may also serve me as priests. With their anointing, Aaron’s descendants are set apart for the priesthood forever, from generation to generation.”

Exodus 40:15 Meaning and Commentary

Exodus 40:15

And thou shall anoint them as thou didst anoint their
father
For Aaron was first anointed, and then his sons:

that they may minister unto me in the priest's office;
which they might not do before their anointing, though separated for it, and called unto it:

for their anointing shall surely be an everlasting priesthood
throughout their generations;
that is, this ceremony of anointing was to be used in all ages at the investiture of the high priest with his office, until the Messiah should come, who would put an end to the Aaronic priesthood; for not common priests, only the successors of the high priest, were anointed in later times; this present unction serving for all the priests that should follow in successive generations, so long as the priesthood continued.

Exodus 40:15 In-Context

13 Dress Aaron with the sacred garments and anoint him, consecrating him to serve me as a priest.
14 Then present his sons and dress them in their tunics.
15 Anoint them as you did their father, so they may also serve me as priests. With their anointing, Aaron’s descendants are set apart for the priesthood forever, from generation to generation.”
16 Moses proceeded to do everything just as the LORD had commanded him.
17 So the Tabernacle was set up on the first day of the first month of the second year.