Anointing of the Sick is that sacrament which is administered to strengthen Christians who are in danger of death from sickness or old age. The Apostle James refers to this sacrament when he says, “Is any among you sick? Let him call for the elders of the church, and let them pray over him, anointing him with oil in the name of the Lord; and the prayer of faith will save the sick man, and the Lord will raise him up; and if he has committed sins, he will be forgiven” (James 5:14-15).
Anointing of the Sick bestows upon the recipient the courage and peace necessary to bear his suffering, forgives his sins, and prepares him for death. On occasion, when spiritually beneficial, the sacrament heals the physical infirmities of the recipient, but this ought not to be expected. Catholic Answers provides a helpful summary of the origin, effects and value of the sacrament.
The Catholic Catechism systematically explains the Anointing of the Sick, with a more thorough exploration of the effects of the sacrament.
For an in-depth treatment of Anointing of the Sick, see the early twentieth century Catholic Encyclopedia article on Extreme Unction (an older name for the Sacrament). The details of the rite in use at that time are outdated, but the discussion of the sacrament's matter and form, along with extensive citations from Scripture and Tradition in support of the Sacrament, are outstanding.
If you only have time to look at three things, LOOK AT THESE.
- Catholic Answers: Anointing of the Sick
- Anointing of the Sick in the Catechism
- A Scholarly Exposition of the Sacrament
And if you've got more time...
The Rite of Anointing was revised in 1972 to give us the Sacrament as we know it today. The nature and reasons for these ritual revisions were made clear by Pope Paul VI in his decree On the Sacrament of the Anointing of the Sick.