Is there any Biblical prophecy mentioning that there will be a sign of the cross put in the sky? Either in the Old Testament or the Book of Revelation?
Thre is no Biblical prophecy about a sign of the cross appearing in the sky. However, some have interpreted Matthew 24:30 to be that sign.
And then shall appear the sign of the Son of man in heaven: and then shall all the tribes of the earth mourn, and they shall see the Son of man coming in the clouds of heaven with power and great glory. (KJV)
The assumption is that the "sign of the Son of man" will be the shape of a cross appearing in the sky.
This belief is bolstered (but not validated) by at least two events.
The emporer Constantine is said to have seen a vision of the cross in the noon-day sky.
Accordingly Constantine called on him with earnest prayer to reveal to him who he was, and stretch forth his right hand to help him in his present difficulties. And while he was thus praying with fervent entreaty, a most extraordinary sign appeared to him from heaven – something which it might have been hard to believe had the story been told by any other person. But since the victorious emperor himself long afterwards declared it to the writer of this history, when he was honored with his acquaintance and society, and confirmed his statement by an oath, who could hesitate to believe it, especially since other testimonies have established its truth? He said that about noon, when the day was already beginning to decline, he saw with his own eyes the sign of a cross of light in the heavens, above the sun, and bearing the inscription, “By this symbol you will conquer.” He was struck with amazement by the sight, and his whole army witnessed the miracle.
In September 1925 what appeared to be a bright cross was seen in the northeast sky above the Church of St. John the Theologian in Athens, Greece.
The form of the Cross itself was an especially dense light and it could be clearly seen as a Byzantine cross with an angular cross bar toward the bottom. This heavenly miracle lasted for half an hour, until midnight, and then the Cross began slowly to raise up vertically, as the cross in the hands of the priest does in the ceremony of the Elevation of the Cross in church. Having come straight up, the Cross began gradually to fade away.
Over the many years the sign of the cross has grown into popular theology, finally embedding itself into the prophecy of Matthew 24. However, you should be aware that there is no theological proof that I'm aware of that the "sign of the Son of man" and the sign of the cross in the sky are or are not the same thing.
Is there any Biblical prophecy mentioning that there will be a sign of the cross put in the sky? Either in the Old Testament or the New Testament?
The closest we can find to such a possible statement comes from Matthew 24:30 in regards to the sign of the Son of Man appearing in the sky.
“Then will appear the sign of the Son of Man in heaven. And then all the peoples of the earth[a] will mourn when they see the Son of Man coming on the clouds of heaven, with power and great glory.
Whether or not the Sign of the Son of Man is the Sign of the Cross is an open question. Personally I do believe it will be the Cross, but that is just me. Nevertheless this interpretation of Matthew 24:30 will possibly remain the Sign of the Cross in popular culture.
Apparitions of the Cross are extremely rare, but are not unheard of in Christian culture.
Constantine at the Milvian Bridge
The first apparition of a sign appearing in the sky to someone is that of Constantine's vision and recorded in the Christian annuals was said to have occurred on October 27, 312 A.D.
It is commonly understood that on the evening of 27 October with the armies preparing for battle, Constantine had a vision which led him to fight under the protection of the Christian God. Some details of that vision, however, differ between the sources reporting it.
Lactantius states that, in the night before the battle, Constantine was commanded in a dream to "delineate the heavenly sign on the shields of his soldiers" (On the Deaths of the Persecutors 44.5). He followed the commands of his dream and marked the shields with a sign "denoting Christ". Lactantius describes that sign as a "staurogram", or a Latin cross with its upper end rounded in a P-like fashion. There is no certain evidence that Constantine ever used that sign, opposed to the better known Chi-Rho sign described by Eusebius.
From Eusebius, two accounts of the battle survive. The first, shorter one in the Ecclesiastical History promotes the belief that God helped Constantine but does not mention any vision. In his later Life of Constantine, Eusebius gives a detailed account of a vision and stresses that he had heard the story from the Emperor himself. According to this version, Constantine with his army was marching (Eusebius does not specify the actual location of the event, but it clearly is not in the camp at Rome), when he looked up to the sun and saw a cross of light above it, and with it the Greek words "Εν Τούτῳ Νίκα", En toutō níka, usually translated into Latin as "in hoc signo vinces". The literal meaning of the phrase in Greek is "in this (sign), conquer" while in Latin it's "in this sign, you shall conquer"; a more free translation would be "Through this sign [you shall] conquer". At first he was unsure of the meaning of the apparition, but in the following night he had a dream in which Christ explained to him that he should use the sign against his enemies. Eusebius then continues to describe the labarum, the military standard used by Constantine in his later wars against Licinius, showing the Chi-Rho sign.
The famous vision of Constantine is commonly believed to have occurred on October 27, 312, sometime in the evening. Constantine saw a Latin cross the upper end rounded like a letter “P”, and a Chi-Ro sign. Thus it had the sign of the cross and the monogram of Christ’s name from the letters “X” and “P”, the first letters of Christ’s name in Greek. Written above this sign were the words ‘In hoc Signo Vinces” (By this sign, you shall conquer). The words appeared to Constantine in Greek. - Battle of the Milvian Bridge
Labarum of Constantine I, displaying the "Chi-Rho" symbol above.
The Holy Cross over Jerusalem (351 A.D.)
Just some 39 years later (351 A.D.), the Cross appeared over Jerusalem The Apparition of the Holy Cross over Jerusalem occurred on May 7, at nine in the morning on the Feast of Pentecost. St. Cyril (315-386), the Patriarch of Jerusalem, was an eyewitness to this glorious event, which lasted for several hours in the sky over the Holy City.
The Precious Cross appeared in the sky over Jerusalem on the morning of May 7, 351 during the reign of the emperor Constantine.
In May of 351 a luminous Cross appeared over Jerusalem, stretching from Golgotha to the Mount of Olives, a distance of about five and a half miles. The Cross was wide as it was long, and shone more brightly than the sun. Many people left their homes and workplaces to gather in the church and glorify Christ. The historian Sozomen says that this wondrous sign led to the conversion of multitudes of pagans and Jews to Christianity.
A letter from Saint Cyril to the emperor describing this phenomenon, and admonishing him to become Orthodox, has been preserved. The apparition of the Cross remained over the city for a whole week.
The vision of the Cross over Jerusalem strengthened the Orthodox faithful and contributed to the return of many Arians to the Church. It is also a reminder of the awesome Second Coming of Christ, when “the sign of the Son of man shall appear in heaven (Matthew 24:30). - Commemoration of the Apparition of the Sign of the Precious Cross Over Jerusalem, in 351 AD
The Apparition of the Holy Cross over Jerusalem is recognized in both the Catholic and Orthodox Churches as a true apparition.
Sign of the Cross Near Athens on September 14, 1925
In 1925, on the eve, of the feast of the Exaltation of the All-Honourable and Life-giving Cross of our Saviour, 14 September according to the Orthodox Church calendar, the all-night vigil was served at the church of St. John the Theologian in suburban Athens.
At 11:30 P.M., there began to appear in the heavens above the church, in the direction of North-East, a bright, radiant Cross of light. The light not only illuminated the church and the faithful but, in its rays, the stars of the clear, cloudless sky became dim and the church-yard was filled with an almost tangible light. The form of the Cross itself was an especially dense light and it could be clearly seen as a Byzantine cross with an angular cross bar toward the bottom. This heavenly miracle lasted for half an hour, until midnight, and then the Cross began slowly to raise up vertically, as the cross in the hands of the priest does in the ceremony of the Elevation of the Cross in church. Having come straight up, the Cross began gradually to fade away. - The Appearance of the Sign of the Cross Near Athens in 1925
Saint Faustina Kowalska from Poland reveals in her writings, a prophecy that the Sign of the Cross will be seen in the heavens shortly before the last day. Although this is in the sphere of private revelation, it holds some weight considering that this Polish nun was canonized by Pope John Paul II on April 30, 2000.
The Sign Of The Cross Will Be Seen In The Sky 83 Write this: Before I come as the just Judge, I am coming first as the King of Mercy. Before the day of justice arrives, there will be given to people a sign in the heavens of this sort:
All light in the heavens will be extinguished, and there will be great darkness over the whole earth. Then the sign of the cross will be seen in the sky, and from the openings where the hands and the feet of the Savior were nailed will come forth great lights which will light up the earth for a period of time. This will take place shortly before the last day.
Holy Cross in Balazar, Portugal
It could be noted that There is at least on apparition of the cross being form on the earth, which is locally known as the Miracle of the Cross. This event occurred on June 21, 1832. "Miraculous signs will occur in the sun, moon, and stars. The nations of the earth will be deeply troubled and confused because of the roaring and tossing of the sea" (Luke 21:25). Might the earth also share in this sign?
The village of Balazar is located 40 miles north of Oporto, made up of small houses of stone with a population of about 1,000 people. The village is surrounded by vineyards and fields of corn, dates and olives. The Church of Balazar is dedicated to the Holy Cross. Erected in 1832, commemorating the mysterious apparition that year of a cross made on the ground. In a report sent to the Archbishop of the Archdiocese of Braga, the pastor of the parish testifies the happenings of that day:
“I’m writing to make you aware of the happenings in the Parish of St. Eulalia de Balasar. During our latest celebration of the Feast of Corpus Christi, the faithful were coming towards the Church and noticed a cross of a lighter color formed on the ground. The morning dew was all over the area, except on the cross. I myself went and touched and moved around the ground where the cross was formed, but the same image reappeared in the same place. Later, I ordered water to be poured over the same area, but the cross reappeared again and it has remained ever since.”