In the Greek Horologion of 1897 the derivation of this Feast is explained:
"Because of the illnesses that occur in August, it was customary, in former times, to carry the Venerable Wood of the Cross through the streets and squares of Constantinople for the sanctification of the city, and for relief from sickness. On the eve (July 31), it was taken out of the imperial treasury, and laid upon the altar of the Great Church of Hagia Sophia (the Wisdom of God). From this Feast until the Dormition of the Most Holy Theotokos, they carried the Cross throughout the city in procession, offering it to the people to venerate. This is the Procession of the Venerable Cross."
Throughout the period of the Dormition Fast beginning on August 1 through the 14th we simultaneously celebrate the Feast of the Procession of the Venerable Wood of the Cross. Unlike the September 14 observance, this commemoration is considered to be a minor feast in comparison and significance, but it does have the bringing out of the Cross and veneration by the faithful like the September feast. It is the first of three "Feasts of the Lord" in the month of August, the other two being the Transfiguration (August 6) and the Icon of Christ "Not Made by Hands" otherwise known as the Holy Mandylion (August 16).
It should be noted that in the Russian Orthodox Church, this feast also celebrates the Baptism of Russia which occurred on August 1, 988. In the "Account of the Order of Services in the Holy, Catholic and Apostolic Great Church of the Dormition", compiled in 1627 by order of Patriarch Philaret of Moscow and All Rus, there is the following explanation of the Feast: "On the day of the Procession of the Venerable Cross there is a church procession for the sanctification of water and for the enlightenment of the people, throughout all the towns and places." Knowledge of the day of the actual Baptism of Rus was preserved in the Chronicles of the sixteenth century: "The Baptism of the Great Prince Vladimir of Kiev and all Rus was on August 1."
It is customary to have a crucession (a procession headed by the Cross) and celebrate the Lesser Blessing of Water on August 1. Because of the blessing of holy water, this holy day is sometimes called "Savior of the Water." The Greeks perform this ceremony on the first of every month, but the Russians do it on August 1 specifically to commemorate the baptism of the Russian people. There may also be celebrated on this day the Rite of Blessing New Honey, for which reason the day is also referred to as "Savior of the Honey".
According to Saint Nikolai Velimirovich in his Prologue explanation of this feast, he adds a few additional significant meanings to this feast:
"This feast was instituted by a mutual agreement of the Greeks and Russians at the time of the Greek Emperor Manuel and the Russian Prince Andrew in commemoration of the simultaneous victories of the Russians over the Bulgarians and the Greeks over the Saracens [in 1164]. In both of these battles, crosses were carried by the armies from which heavenly rays shone. It was therefore instituted that, on August 1, the Cross be carried first to the middle of the Church of the Divine Wisdom [Hagia Sophia] and after that, along the streets for the people to venerate as a commemoration of the miraculous help of the Cross in previous battles. This was not an ordinary cross but the true Honorable Cross which was kept in the church of the imperial court. On July 31, the Honorable Cross was carried from the imperial court to the Church of the Holy Wisdom of God and from there it was carried along the streets for the consecration of the earth and the air. Finally, on August 14, it was again returned to the church of the imperial palace."
Though there are some truth to the words of St. Nikolai concerning the origins of this feast in Russia, in actuality this feast dates much earlier for the Romans of Constantinople. This is clarified by Bulgakov who describes this miraculous event that happened at the same time between two Orthodox armies as a seperate feast from the older Procession of the Venerable Cross. In fact, we know that the origin of the Feast of the Procession of the Venerable Cross goes back to the 9th century or earlier. Russia began to celebrate it at the beginning of the 15th century. The commemoration of the mutual victories of the Russian and Roman armies with the aid of the Cross dates back to the date of the actual battle in 1164.
To better understand the origins and rubrics of the celebration of this feast among the Romans of Constantinople, I refer you to the following information provided within the excellent article by Holger A. Klein titled "Sacred Relics and Imperial Ceremonies at the Great Palace of Constantinople". He writes:
"The Persian invasion of Syria-Palestine in 614 and the Arab conquest of Jerusalem in 637/38 resulted in a number of important relic translations during the reign of Emperor Herakleios (610-641) and changed Constantinople’s status as a repository of sacred relics for centuries. As suggested by the Chronicon Paschale, the relic of the Holy Lance, Sponge, and the True Cross from Jerusalem were recovered from the Persians during the fall of 629, transferred to the capital, and exhibited for public veneration in the church of Hagia Sophia for several days. While Emperor Herakleios, according to some sources, triumphantly returned the relic of the True Cross from Constantinople to Jerusalem and exalted it in the Church of the Holy Sepulcher on 21 March of the following year, the unexpected loss of the Holy City to the Arabs soon necessitated the relic’s transfer back into the capital, where it was now safeguarded by the emperor and kept inside the confines of the imperial palace.
"The forced relocation of the ‘larger part’ of the relic of the True Cross from Jerusalem to Constantinople and its presumed deposition in the imperial palace not only ensured the Empire’s safety and prosperity for the future, it also re-affirmed the emperor’s role as the guardian and protector of Christianity’s most sacred treasure. While a smaller portion of the relic, associated with Constantine the Great and set in a bejeweled processional Cross, had already been used in imperial processions in the beginning of the sixth century, and is known to have preceded the imperial army on military campaigns during the reign of Emperor Maurice, it was the alleged return of the True Cross from Jerusalem that effectively transformed Constantinople into a ‘New Jerusalem’ and the imperial palace into a locus sanctus at the heart of the Empire. The possession of the True Cross not only reinforced the emperor’s divine mandate but also rendered him the most important distributor of relics of the True Cross in the Christian world, a position future emperors would eagerly exploit in building political alliances with Christian rulers and potentates in Western Europe.
"Where the relic of the True Cross from Jerusalem was originally kept cannot be determined with certainty. In the second half of the seventh century, when Bishop Arkulf visited Constantinople on his way back from the Holy Land, a portion of the relic was, at least for the time of its public veneration during Holy Week, kept inside Hagia Sophia in a 'very large and beautiful chest [...] to the north of the interior of the building.' Arkulf’s testimony has often been considered as an indication that the main relic of the True Cross had, by the seventh century, been entrusted to the care of the Patriarch. Judging from later accounts, however, it is more likely that the relic of the True Cross from Jerusalem and the so-called ‘Cross of Constantine’, first mentioned by Theodore Anagnostes, were both safeguarded inside the imperial palace, presumably in the skeuophylakion, and removed only temporarily for specific liturgical and ceremonial functions. As recorded in Constantine VII Porphyrogennetos’ Book of Ceremonies [10th cent.], important relics of the True Cross were still kept in the skeuophylakion of the imperial palace during the tenth century and taken out on specific feasts and occasions. One such feast was a six-day-long festival celebrated in mid-Lent that included a public display and veneration of the relic of the True Cross inside Hagia Sophia and a related imperial ceremony performed in the palace.
"According to the Book of Ceremonies, celebrations started on the third Sunday of Lent in the skeuophylakion of the imperial palace. Between the third and sixth ode of Orthros [Matins], the 'three glorious and life-giving Crosses', were removed from the treasury, embalmed by the protopapas, and taken to the Nea Ekklesia, to be venerated by all. After Orthros was concluded, the Crosses were taken to the gallery of the church, where the clergies of the Nea and the imperial palace jointly intoned the troparia of the Crucifixion. At this time, the emperor and his co-emperors were given the opportunity to venerate and kiss the precious and life-giving relics. Then, the three Crosses were separated from each other. Accompanied by the clergy of the Nea, a deacon carried one of them back down to the main level of the church to be displayed for further veneration. The second Cross was taken over by the papias of the Great Palace, who, accompanied by the palace clergy, the protopapas of the church of St. Stephen, and the diaitarioi of the palace, carried it in festive procession through the Heliakon [of the Chrysotriklinos] and from the Chrysotriklinos into the Lausiakos, where it was displayed for the veneration by members of the senate. The Cross was then taken to the Church of the Protomartyr Stephen in the Daphne palace, where it remained over night. On the following day, the papias took the relic to Hagia Sophia, where it was displayed for veneration by the faithful during the rest of the week. The third Cross never left the gallery of the Nea. After none on Friday, when public venerations had ended at Hagia Sophia, the papias and the clergy of the Nea brought the respective Crosses back into the palace. Finally, between the third and sixth ode of Orthros on Sunday, the protopapas and the skeuophylax returned all Crosses to the skeuophylakion.
"What is striking about this description is not only the fact that, by the tenth century, three Crosses of the glorious and life-giving Wood, were kept in the skeuophylakion of the imperial palace, but also that these relics were employed in a complex ceremony that involved their display in three distinct locations within the imperial palace – the Nea Ekklesia, the Lausiakos, and the Church of St. Stephen – as well as in the church of Hagia Sophia.
"Another, closely related ceremony involving the True Cross is described in the Book of Ceremonies for the week before and the two weeks following August 1. Once again, the ceremony started between the third and sixth ode of Orthros in the skeuophylakion of the palace. After the relic was embalmed, it was taken to an unspecified church within the imperial palace, where it was displayed for veneration by the emperors. The relic was then taken to the Lausiakos, where it was set up to be venerated by the members of the senate. Afterwards, the Cross was taken to the church of St. Stephen, from where it was carried through each of the quarters of the capital to 'cleanse and sanctify all places and houses of the God-guarded and imperial city; and not only the buildings, but also the walls of the city and its suburbs.' When the relic returned from its journey on August 13, it was first brought to the Chrysotriklinos and placed on the imperial throne. Then, the papias, accompanied by the protopapas and the clergy, took the relic through the rooms of the imperial palace to cleanse and sanctify them as well. For a short while thereafter, the relic was kept in the oratory of St. Theodore, before the papias carried it back to the Church of the Virgin of the Pharos after Vespers. Here, the relic was received by the skeuophylax of the palace and returned to the treasury between the third and sixth ode of Orthros."
Apolytikion in the First Tone
O Lord, save Your people, and bless Your inheritance. Grant victories to the Orthodox and over their adversaries; and preserve your habitation by virtue of Your Cross.
Kontakion
As You were voluntarily raised upon the Cross for our sake, grant mercy to those who are called by Your Name, O Christ God; make all Orthodox Christians glad by Your power, granting them victories over their adversaries, by bestowing on them the invincible trophy, Your weapon of peace.
HYMN OF PRAISE TO THE HONORABLE CROSS OF CHRIST
By Saint Nikolai Velimirovich
(For the Feast of the Procession of the Venerable Cross)
The Honorable Cross of Christ
Before it, all honorably prostrate,
By the power of the Cross of Christ
From temptation, we are redeemed.
The Holy Cross is mightier than the demons
And from every earthly king,
From sickness, the Cross saves
And from the assaults of barbarians.
Prince Andrew, by the power of the Cross
Enslaved lands, saved;
King Manuel, by the power of the Cross
The Saracens, gloriously destroyed.
From the armies of pagans,
From the tyrannical conquerors,
From all evils demonstrated that
The power of the Cross is mightier.
The Honorable Cross of Christ
Before it, all honorably prostrate,
By the power of the Cross of Christ
From temptation, we are redeemed.
The Holy Cross is mightier than the demons
And from every earthly king,
From sickness, the Cross saves
And from the assaults of barbarians.
Prince Andrew, by the power of the Cross
Enslaved lands, saved;
King Manuel, by the power of the Cross
The Saracens, gloriously destroyed.
From the armies of pagans,
From the tyrannical conquerors,
From all evils demonstrated that
The power of the Cross is mightier.