The sakkos (from the Greek: σάκκος, “sackcloth”) is a vestment worn by Orthodox bishops instead of the priest’s phelonion. The bishop wears the sakkos when he celebrates the Divine Liturgy and other services when called out by the rubrics.
Originally, all bishops wore a phelonion similar to the one worn by priests, but woven or embroidered with a multilayered cross pattern called the polystavrion ("many-crosses"). The use of the sakkos was a privilege bestowed by the Basileus (Emperor) upon individual patriarchs as a sign of his personal favor. The first literary evidence for the garment is found in the twelfth century writings of Balsamon, Patriarch of Antioch. By the thirteenth century the sakkos was worn by all the patriarchs as well as a few high-ranking archbishops. Other bishops continued to wear the polystavrion. After the fall of Constantinople in 1453 wearing the sakkos came into general use by bishops. The sakkos is now worn by all Orthodox, as well as Byzantine rite Roman Catholic. bishops regardless of rank.
The garment is a tunic with wide sleeves, and a distinctive pattern of trim. It reaches below the knees and is fastened up the sides with buttons or tied with ribbons. It is similar in form to the western dalmatic, which is similarly derived from Byzantine dress. The sakkos was originally worn by the Emperor as an imperial vestment, symbolizing the tunic of disgrace worn by Christ during his trial and mockery.
The sakkos is usually made of a rich brocade fabric and may be intricately embroidered. There is normally a cross centered on the back, which the bishop kisses before it is placed on him. Buttons or loops are sewn on the back, by which the bishop's omophorion (either great or small) may be attached. Traditionally, bells are attached to the sakkos, following the biblical directions for the vestments of the Jewish High Priest (Exodus 28:33-34; 39:25-26).
The bishop wears the sakkos when he vests fully to celebrate the Divine Liturgy, at the Great Doxology at Matins when there is an All-Night Vigil, or on specific other occasions when called for by the rubrics such as, at the bringing out of the epitaphios on Great and Holy Friday or the cross on the Great Feast of the Exaltation of the Holy Cross. At other services, he wears the episcopal Mantle (in Greek: Μανδύας, Mandýas, in Old Church Slavonic: Mantiya).
When the bishop is vested, which in the Russian tradition takes place in the middle of the nave, the sakkos is presented to him on a tray. He blesses it with both hands, and two subdeacons lift the sakkos off the tray, hold it for him to kiss the cross on the back, place it on him, and button the sides. The epigonation, which was placed on the bishop earlier, is lifted up as the sakkos is buttoned, so that it remains visible on the outside of the sakkos. During the vesting of the sakkos, the protodeacon swings the censer and chants the Prayer of the Sakkos:
Thy high priests shall be clothed in glory, and Thy saints shall rejoice with joy, always, now and ever, and unto the ages of ages. Amen.
This prayer is identical to that used by a priest when he vests in the phelonion, except that instead of saying "Thy high priests", a priest says simply, "Thy priests".
In some traditions, a bishop may choose to celebrate the Liturgy "as a priest"; meaning he does not vest in full episcopal vestments, nor does he make use of the dikirion and trikirion (liturgical candlesticks). Then, instead of the sakkos he wears a priestly phelonion, with only the small omophorion on his shoulders and the epigonation at his side. The bishop will in this instance, as always, wear his Panagia engolpion, and will stand on the orlets (eagle rug). Also, certain ceremonial practices are not observed as they would be for a full hierarchal service.