The biblical foundation for the sacrament of holy anointing is found in Mark 6:7-13 and James 5:14-15. The earliest Christian writers knew those verses and this sacrament well. We suggest you read the verses before reading on.
Origen
“[T]here is also a seventh [method of forgiveness for the sinner] . . . when he 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 [ca. A.D. 250]).
Aphraates
“[F]rom the glistening olive fruits are put forth [that is, olive oil], in which there is a sign of the sacrament of life, by which Christians are perfected, as well as priests and kings and prophets. It illuminates the darkness, anoints the sick, and leads back penitents in its secret sacrament” (Treatises 23:3 [A.D. 345]).
Serapion
“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 from heaven the healing power of the only-begotten [Son] upon this oil, so that for those who are anointed . . . it may be effective for the casting out of every disease and every bodily infirmity, and for an antidote against every demon, for escape from every unclean spirit, for the expulsion of every evil spirit, for the banishing of every fever and chill and every weakness, for good grace and remission of sins, for a remedy unto life and deliverance, for health and integrity of soul, of body, and of spirit, for perfect vigor” (The Sacramentary of Serapion 29:1 [ca. A.D. 350]).
John Chrysostom
“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]).
Ambrose
“Why, then do you [Donatists, who deny the sacrament of penance] impose hands and believe it to be the effect of the blessing if perchance some sick person recovers? Why do you presume that any can be cleansed by you from the filth of the devil? Why do you baptize, if it is not allowed that sins be forgiven through men? In baptism too there is forgiveness of sins; what is the difference whether priests claim this power is given them to be exercised in penance or at the font? The mystery is the same in both” (On Penance 1:8:36 [ca. A.D. 388]).
Pope Innocent I
“Celestine, the deacon, has also added in his letter that [you have] raised a question concerning what was written in the epistle of the blessed apostle James: ‘If there is anyone sick among you, let him call in the presbyters and let them pray over him, anointing him with oil in the name of the Lord; and the prayer of faith will save the sufferer, and the Lord will raise him up, and if that man has committed sin, he will forgive him.’ There is no doubt that this is to be taken or understood in regard to the sick faithful, who are able to be anointed with the holy oil of chrism, which, having been confected by a bishop, is permitted not only to priests but also to all as Christians . . . But it cannot be administered to penitents, because it is a kind of sacrament. For how should it be supposed that one kind of sacrament could be granted to those who are denied the other sacraments?” (Letters 25:8:11 [A.D. 416]).
Ceasar of Arles
“As often as some infirmity overtakes a man, let him who is ill receive the Body and Blood of Christ; let him humbly and in faith ask the presbyters for blessed oil, to anoint his body, so that what was written may be fulfilled in him: ‘Is anyone among you sick? Let him bring in the presbyters, and let them pray over him, anointing him with oil; and the prayer of faith will save the sick man, and theLord will raise him up; and if he be in sins, they will be forgiven him.’ See to it, brethren, that whoever is ill hasten to the church, both that he may receive health of body and will . . . obtain the forgiveness of his sins” (Sermons 13:3 [ca. A.D. 522]).