What is the sign of the Son of Man?

Question

What is the sign of the Son of Man spoken of in Matthew 24:30?—

At that time the sign of the Son of Man will appear in the sky, and all the nations of the earth will mourn. They will see the Son of Man coming on the clouds of the sky, with power and great glory.

Edit: As per Jon's comment here is what I have in mind—

• It could be the cross. But that is only my intuition. What would be the support for such a position?
• It could be something else revealed in the scripture that I don't know. For example, the number of man is given in the Scripture. Maybe this is too.
• Maybe I'm understanding it wrong and it doesn't mean a physical sign appearing in the sky but something symbolic.

Answer 1

I have encountered so many views on what this means that I have concluded nobody definitely knows. This is not to be unexpected because prophecy, although leading people to a certain true yet ‘vague impression’ of what will occur, is not completely clear, until it does occur. One can easily verify this, as even the disciples could not believe Christ would fulfill prophecy by dying at the hands of the Jewish leaders and Romans until it actually occurred.

I am among those who understand the verses mentioned almost immediately before as indicating the destruction of Jerusalem, which may have been like ‘a sign from heaven’, but this particular verse is now speaking about the end of the world. The historic event does not fully answer the question.

The only speculation, that I feel is possibly true, is that the sign is the miraculous prediction of the majority of the Jewish nation converting to Christianity, so as to overwhelmingly shock the world. This would indeed be a miraculous sign; proving Jesus is the Messiah. This would occur shortly before (in terms of total world history) he actually returns in judgment in the same manner that he left, ‘in the clouds’. Paul also seems to speak of this miraculous future event:

Again I ask: Did they stumble so as to fall beyond recovery? Not at all! Rather, because of their transgression, salvation has come to the Gentiles to make Israel envious. But if their transgression means riches for the world, and their loss means riches for the Gentiles, how much greater riches will their full inclusion bring! (NIV Romans 11:11)

Think about it, if the Gentiles taking on a Jewish religion, while the Jews rejected it, was so overwhelming as to topple Rome, the world’s greatest power, how much more will their predicted ‘full inclusion’ wipe away so many other kingdoms of philosophy, religion, etc. It will be the greatest sign on heaven since his resurrection after three days. Assuming that this sign is referring to this event of course.

Answer 2

I can't help but chip in from a linguistics and physical point of view.

I observe that σημείο is occasionally misunderstood as miracle. Like Signs and Wonders.

However, I tend to believe that the word actually correlates to being a signature token.

The implied meanings of signature token should be

• proof of identity
• identifying characteristics
• a pattern of events or phenomenon that identifies a point in time
• a token that can be used for identity or proof

On the whole, it actually engages in providing identity or identification of person/event/phenomenon/entity.

It can be misunderstood to mean miraculous because there would be instances where the identity of the person/event is either divine or phenomenally impossible that it would take a miracle to provide the identity.

What it can be correlated to in modern greek

• a point in Cartesian coordinates
• a location on a map
• an identity point in the space-time
• an identity point in temperature, pressure, etc. e.g. Freezing Point of water, the point at which Pressure - Temperature - Volume meet in a PVT diagram.
• a point in reasoning, a purpose of a concept
• an agendum (Side Note: in English agenda = plural number of singular agendum. Whereas agendas would mean the different sets of agenda.)
• an expectation or expected action item or consequence of an agendum.

Therefore, σημείο in the passage describes a set of events and phenomenon that would occur where the characteristics are so compelling, unique and identifying that as to make it impossible to deny the identity or purpose or concept of "the son of man".

Perhaps, thus far a hidden agendum that would be revealed at that particular point in time and space. An agendum which you have no supposed means to predict or comprehend until then. An agendum finally being revealed that would be so devastating to the point of existence of humankind, that they would weep and mourn. Pertaining to the great question of - What is the point of the human race. Such that the agendum is so contrary and devastating to the expectations of all humans.

Answer 3

Right off the bat, Jesus is making an allusion to Daniel:

I saw in the night visions,

and behold, with the clouds of heaven
    there came one like a son of man,
and he came to the Ancient of Days
    and was presented before him.
And to him was given dominion
    and glory and a kingdom,
that all peoples, nations, and languages
    should serve him;
his dominion is an everlasting dominion,
    which shall not pass away,
and his kingdom one
    that shall not be destroyed.

—Daniel 7:13-14 (ESV)

His favorite self-designation was "Son of Man", which on the surface means that he was human. But by connecting the title with this passage, it also shows that he intended to establish the final kingdom which will outlast all others. The sign was actually a person, "one like a son of man", in Daniel. It seems like the same is true in Matthew:

Then will appear in heaven the sign of the Son of Man, 
    and then all the tribes of the earth will mourn, 
and they will see the Son of Man coming on the clouds of heaven 
    with power and great glory.

—Matthew 24:30 (ESV)

I reformatted the text to show parallel structure: the Son of Man is the sign. The "tribes of the earth will mourn" because of His "power and great glory". This mourning is also an allusion back to Daniel:

As for me, Daniel, my spirit within me was anxious, and the visions of my head alarmed me.—Daniel 7:15 (ESV)

and

Here is the end of the matter. As for me, Daniel, my thoughts greatly alarmed me, and my color changed, but I kept the matter in my heart.—Daniel 7:28 (ESV)

The coming kingdom is alarming because it signals the end of existing kingdoms.

Preterist View

Because Jesus warns that these events are eminent ("Truly, I say to you, this generation will not pass away until all these things take place."—Matthew 24:34), one view of the text is that Jesus returned sometime during the first century. This wouldn't be the cross or his resurrection, however, since it seems clear that these events will happen after the events recorded in Matthew. (See also Matthew 16:21-28.) So the most likely guess is the destruction of the Temple in 70 AD.

This interpretation implies that the Roman Empire is the final kingdom, so some preterists conclude that the Parousia is still in the future. Others see the destruction of the Temple in Jerusalem as clearing away the previous system and the establishment of the Church as the final system of reconciliation with God.

Futurist View

Most other interpretations of the passage presume that the Son of Man will appear suddenly and visibly to everyone at once sometime in the future. Two possible parallels would be the star that announced Jesus' birth to the astrologers in Matthew 2 and the angels who announced the birth in Luke 2. But instead of pointing to a human child, the sign would be the coming King Himself: