Exodus 40:15

15 And put oil on them as you did on their father, so that they may be my priests: the putting on of oil will make them priests for ever, 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 You are to put on Aaron the holy robes; and you are to put oil on him, and make him holy, so that he may be my priest.

14 And take his sons with him and put coats on them;

15 And put oil on them as you did on their father, so that they may be my priests: the putting on of oil will make them priests for ever, from generation to generation.

16 And Moses did this; as the Lord gave him orders, so he did.

17 So on the first day of the first month in the second year the House was put up.