“Lord, endow me with the garment of salvation, the vestment of joy, and with the dalmatic of justice ever encompass me .”
(Vesting prayer while putting on the dalmatic).
The outermost vestment of the deacon is the dalmatic, a knee length garment with sleeves, “The vestment proper to the deacon is the dalmatic, worn over alb and stole.” (GIRM 338).
The dalmatic is an ancient vestment, originally from Dalmatia, associated with a servant and its origins are thought to be similar to that of the alb over time becoming shorter and acquiring wider sleeves and ornamentation. It has changed little and this perhaps reflects the fact that a deacon was not a common sight before the reforms of the Second Vatican Council.
Although most commonly associated with the diaconate, a deacon is not the only ordained minister to wear a dalmatic. When he celebrates a solemn Mass on a major occasion the bishop wears a pontifical dalmatic beneath his chasuble. This is a light garment, either white or the colour of the vestments. He wears as a sign of the fullness of Orders represented by his role as bishop – there are three ordained ministries in the Catholic Church: deacon, priest and bishop, and the bishop, by being a bishop, represents all three because he has been ordained to all three. Once you are ordained it is for life. This is why, when a bishop celebrates a Confirmation or other Mass seven candles are lit on the altar.
The dalmatic, and the deacon’s stole underneath it, always match the vestments worn by the priest and change according to the season or feast being celebrated.