Church Fathers: Holy Unction

“The priests of Judaism had power to cleanse the body from leprosy—or rather, not to cleanse it at all, but to declare a person as having been cleansed. . . . Our priests have received the power not of treating with the leprosy of the body, but with spiritual uncleanness; not of declaring cleansed, but of actually cleansing. . . . Priests accomplish this not only by teaching and admonishing, but also by the help of prayer. Not only at the time of our regeneration [in baptism], but even afterward, they have the authority to forgive sins: ‘Is there anyone among you sick? Let him call in the priests of the church, and let them pray over him, anointing him with oil in the name of the Lord. And the prayer of faith shall save the sick man, and the Lord shall raise him up, and if he has committed sins, he shall be forgiven.’”
(On the Priesthood 3:6:190ff [A.D. 387])
“We beseech you, Savior of all men, you that have all virtue and power, Father of our Lord and Savior Jesus Christ, and we pray that you send down from heaven the healing power of the only-begotten [Son] upon this oil, so that for those who are anointed . . . it may be effected for the casting out of every disease and every bodily infirmity . . . for good grace and remission of sins . . . ”
(The Sacramentary of Serapion 29:1 [A.D. 350]).
“[The penitent Christian] does not shrink from declaring his sin to a priest of the Lord and from seeking medicine . . . [of] which the apostle James says: ‘If then there is anyone sick, let him call the presbyters of the Church, and let them impose hands upon him, anointing him with oil in the name of the Lord; and the prayer of faith will save the sick man, and if he be in sins, they shall be forgiven him.”
(Homilies on Leviticus 2:4 [A.D. 250]).