Oil is frequently mentioned in the Old Testament in connection with the commissioning of priests, prophets and kings. It is celebrated in the psalms as a sign of joy and gladness, and even the olive branch brought back by Noah's dove in Genesis, as a sign of the flood's end, was seen by the early Church Fathers as a sign of the peace and new life that sacramental anointing would bring in the New Covenant. Likewise, the descent of the Spirit upon Christ after His Baptism in the river Jordan was taken to be the fulfilmment of the promise that the Messiah would be anointed "with the oils of gladness" (Psalm 45:8). Christ sent His Apostles to anoint the sick (Mk. 6:13), and the Apostle James tells the sick to have the presbyters of the Church do the same (Jas. 5:14-15).
Every year, at the Chrism Mass, the bishop blesses the Oil of Catechumens, and the Oil of the Sick, and consecrates the Sacred Chrism. The Chrism Mass has traditionally been celebrated on Holy Thursday in the morning, but recent reforms suggest that it may be celebrated on a day prior to Holy Thursday.
Chrism is pure olive oil mixed with balsam or perfume. Holy Chrism is used to anoint the newly baptized, to seal the candidates for Confirmation and to anoint the hands of priests and the heads of bishops at their ordination. This oil is also used for the blessing of bells and for consecrating churches, altars, chalices and patons.
The Oil of Catechumens, is used with candidates for Baptism in the ceremonies and prayer and exorcism prior to Christian Initiation and is also used to anoint infants prior to their baptism.
The Oil of the Sick, which a priest may bless in cases of necessity, is used as its name indicates, to bring comfort and support to the infirm in the sacrament of the Anointing of the Sick.
The holy oils are kept in vessels called "stocks" or ampullae and are stored in an "ambry".
[Source: Supplement to the Sunday Bulletin of February 3, 2008; St. Paul Parish, Saskatoon, SK, Canada.]