Tertullian — Against Praxeas 7

After this, when we have issued from the font, we are thoroughly anointed with a blessed unction, — (a practice derived) from the old discipline, wherein on entering the priesthood , men were wont to be anointed with oil from a horn, ever since Aaron was anointed by Moses . Whence Aaron is called Christ, from the chrism, which is the unction; which, when made spiritual, furnished an appropriate name to the Lord, because He was anointed with the Spirit by God the Father; as written in the Acts: For truly they were gathered together in this city against Your Holy Son whom You have anointed. Thus, too, in our case, the unction runs carnally, ( i.e. on the body,) but profits spiritually; in the same way as the act of baptism itself too is carnal, in that we are plunged in water, but the effect spiritual, in that we are freed from sins .