As a Christian symbol it is of very frequent occurrence in ancient ecclesiastical art.
As a symbol of the Holy Spirit it appears especially in representations of the baptism of Our Lord (Matthew 3:16) and of Pentecost. St. Gregory the Great (590-604) is generally shown with a dove on his shoulder, symbolizing inspiration or rather Divine guidance. A dove of gold was hung up in the baptistery at Reims after the baptism of Clovis; in general the symbol occurs frequently in connexion with early representations of baptism. In ancient times a dove-like vessel was frequently suspended over the baptismal font and in that case
As a symbol of martyrdom it indicated the action of the Holy Spirit in bestowal of the fortitude necessary for the endurance of suffering.
As a symbol of the Church, the agent through which the Holy Spirit works on earth. When two doves appear the symbolism may represent, according to Macarius (Hagioglypta, 222), the Church of the circumcision and that of the Gentiles.
On a sarcophagus or on other funeral monuments the dove signifies:
the peace of the departed soul, especially if, as is often the case in ancient examples, it bears an olive branch in its beak;
the hope of the Resurrection.
In each case the symbolism is derived from the story of Noah and the Flood. Such is the meaning of the dove (columbula, palumba sine felle) in numerous epitaphs of the Roman catacombs. Occasionally funeral lamps were made in the shape of a dove. Two doves on a funeral monument sometimes signify the conjugal love and affection of the parties buried there. The dove in flight is the symbol of the Ascension of Christ or of the entry into glory of the martyrs and saints (cf. Psalm 123:7: "Our soul is escaped as a bird from the snare of the hunters, the snare is broken and we are delivered." In like manner the caged dove signifies the human soul yet imprisoned in the flesh and held captive during the period of mortal life. In general, the dove as a Christian emblem signifies the Holy Spirit either personally or in His works. It signifies also the Christian soul, not the human soul as such, but as indwelt by the Holy Spirit; especially, therefore, as freed from the toils of the flesh and entered into rest and glory.
As a Eucharistic vessel
The reservation of the Holy Eucharist for the use of the sick was, certainly since early medieval times, effected in many parts of Europe by means of a vessel in the form of a dove, suspended by chains to the baldachino and thus hung above the altar. Mention may be made here of the (two) doves occasionally represented in the Roman catacombs as drinking from a Eucharistic chalice (Schnyder, "Die Darstellungen des eucharist. Kelches auf altchr. Grabinschriften", in "Stromation Archaeologicon", Rome, 1900, 97-118). The idea of the Eucharistic vessel was probably taken from the dove-like receptacle used at an early period in the baptisteries and often suspended above the fonts. These vessels were usually made of gold or silver. This was no doubt always the case if the vessel was designed to be the immediate holder of the Blessed Sacrament, since the principle that no base material ought to be used for this purpose is early and general. But when, as seems generally to have been the case in later times, the dove was only the outer vessel enshrining the pyx which itself contained the Blessed Sacrament, it came about that any material might be used which was itself suitable and dignified. Mabillon (Iter Ital., 217) tells us that he saw one at the monastery of Bobbio made of gilded leather, and one is shown to this day in the church of San Nazario at Milan which is enameled on the outside and silver gilt within. The exact time at which such vessels first came into use is disputed, but it was certainly at some early date. Tertullian (C. Valentinian. cap. iii) speaks of the Church as columbae domus, the house of the dove, and his words are sometimes quoted as exhibiting the use of such vessels in the third century. The reference, however, is clearly to the Holy Spirit. In the life of St. Basil, attributed to St. Amphilochius, is perhaps the earliest clear mention of the Eucharistic dove. "Cum panem divisisset in tres partes . . . tertiam positam super columbam auream, desuper sacrum altare suspendit" (When he had divided the bread into three pieces . . . the third part placed in a golden dove, he suspended, etc., Vita Bas., P.G., XXXIX). St. Chrysostom's expression concerning the Holy Eucharist, convestitum Spiritu Sancto, clothed with the Holy Spirit (Hom. xiii, ad pop. Antioch.), is generally taken to allude to this practice of reserving the Holy Eucharist in a dove, the emblem of the Holy Spirit. The same idea is expressed by Sedulius (Epist. xii) in the verses, "Sanctusque columbae Spiritus in specie Christum vestivit honore" -- "And the Holy Spirit in the form of a dove has robed Christ in honour".
The general, and certainly the earliest custom, both East and West, was to suspend the dove from the ciborium or baldachino. At a later period in some parts of the West, especially in Rome, a custom grew up of placing a tower of precious material upon the altar, and enclosing the dove with the Blessed Sacrament within this tower. Thus, in the "Liber Pontificalis" which contains ample records of the principal gifts made to the great basilicas in the fourth and succeeding centuries, we never find that the dove was presented without the tower as its complement. Thus in the life of Pope Hilary it is said that he presented to the baptistery at the Lateran turrem argenteam . . . et columbam auream. In the life of St. Sylvester (ibid.) Constantine is said to have given to the Vatican Basilica pateram . . . cum turre et columba. Innocent I (ibid.) gave to another church turrem argenteam cum columba.