Liturgical Handbook of the Russian Orthodox Church Abroad
For those appointed to wear it (which includes all Deacons and Priests), the ryassa — the wide-sleeved outer garment worn over the cassock — is always worn in the church unless it is superseded by the Priest or Deacon donning full liturgical vestments. Except in cases of exceptional necessity, a cleric never enters the temple at all during any liturgical or pastoral context without wearing his ryassa (i.e. wearing only his cassock); and most certainly, the cleric never dons ‘lesser vestments’ (i.e. stole, cuffs and phelon for lesser services) merely over a cassock, under any circumstances, but always over a ryassa — this includes the hearing of confessions, which must be done in a ryassa with the appropriate vestments, as Holy Confession is a sacramental act administered by a properly vested Priest, not an informal conversation undertaken in street clothes. (We take note that the incorrect practice of doing many things in a cassock only, for example, celebrating the All-Night Vigil in lesser vestments donned solely over a cassock without a ryassa, is especially prevalent in certain other jurisdictions in Europe. We must stress that according to the customs of the Church Abroad this is entirely inappropriate and must never be emulated. This applies also to visiting clergy in temples of the Church Abroad: if such a cleric arrives without a ryassa for a Divine Service, he must be provided with one ‘on loan’ from the local cleric, or must not serve.)
The exception to this rule is when a Priest or a Deacon enters the temple outside of a liturgical or pastoral context, in order, for example, to clean the Altar or perform other such works for which wearing a ryassa would not be appropriate.
The ryassa is also worn by the Priest and Deacon in all formal circumstances of priestly life. It should be worn, for example, when teaching a parish class or catechism lesson, when chairing a parish council meeting, at formal meals in a parish hall or similar venue, when speaking at a public engagement or representing the Church in a cultural or social setting, etc.; and all Priests and Deacons always wear the ryassa in the presence of a Bishop, whatever or wherever that may be, unless he invites them to do otherwise.
Bishops themselves follow the same rules for the wearing of the ryassa, and are never in the Altar in the cassock alone, nor in any formal Church activity or engagement. At times a Bishop may elect to lessen this rule in non-liturgical settings (for example, eating at an informal meal without a ryassa), and may invite the clergy present with him to do likewise; however, this should not be presumed, even if the Bishop himself should remove his own ryassa, unless and until he formally invites the other clergy to do similarly.
