Once, as Jesus was going out of the temple in Jerusalem, His disciples took note of the buildings. Jesus used that moment to tell them about what would happen in the future, including addressing what is the sign of the Son of Man (Matthew 24:30). This was the setting of Jesus’ prophetic discourse on the Mount of Olives, perhaps better known as the Olivet Discourse (Matthew 24).
As the disciples pointed out the buildings of the temple complex (Matthew 24:1), Jesus remarked that every stone would be torn down (Matthew 24:2). The disciples in their curiosity asked Him two questions: 1) when these things would happen and 2) what would be the sign of His coming and the end of the age (Matthew 24:3). Jesus responded with a foretelling of things that would take place, and He acknowledged that there would indeed be the sign of the Son of Man (Matthew 24:30).
First, Jesus cautions them not to be misled by false messiahs or to think that they had entered the final days of the age (Matthew 24:4–8). Wars and rumors of wars, famines, and earthquakes would be merely the beginning of “birth pangs” leading up to the end. The disciples would undergo persecution and death and would be hated by all because of the name of Jesus (Matthew 24:9). That still wouldn’t be the end, though. Many would fall away, betrayal and hatred would increase, and false prophets would arise (Matthew 24:10–11). Lawlessness would increase, and love would grow cold (Matthew 24:12). Jesus adds that the one who endures to the end would be delivered and that the good news of the coming kingdom would be proclaimed throughout all the nations. It would be then that the end would come (Matthew 24:13–14). Comparing some other passages with the Olivet Discourse, we see that Jesus moves in His narrative from describing an unstated amount of time to a three-and-a-half-year period leading up to the sign of the Son of Man.
Jesus warns that, when people see the abomination of desolation, they should flee to the mountains. This abomination is described in Daniel 9:27, 11:31, and 12:11 as taking place in the midpoint of the final seven years of the prophetic calendar. That event will herald a great tribulation unlike anything before or after (Matthew 24:15–21). Jesus tells the disciples these things ahead of time so they will not be misled by false prophets and false messiahs, some of whom will even show great signs and wonders (Matthew 24:23–26). When Jesus returns to the earth to establish His kingdom, it will be obvious to all—like lightning that flashes across the sky (Matthew 24:27). After that time and the dreadful events that take place, the heavens will be greatly disturbed (Matthew 24:29), and then the sign of the Son of Man will appear (Matthew 24:30). All people will see Him coming with power and glory (Matthew 24:30), and He will return.
In this context Jesus does not explain what exactly is the sign of the Son of Man, and the disciples do not ask for any further explanation. Earlier, the Pharisees, after making their rejection of Jesus clear, had demanded yet another sign from Jesus, and He explained they would have no further sign but the sign of Jonah, which pointed to the Messiah being buried for three days (Matthew 12:38–40). Again, they demanded a sign in Matthew 16:1, and He again affirmed that they would only get the sign of Jonah. The false messiahs and false prophets would perform signs to deceive people into thinking they were authentic, but the true sign pointing to the Son of Man—the rightful Messiah King—would not be evident until the right time. It seems even by the disciples’ question that they understood that Jesus’ coming again was itself the sign. It was the proof, the miracle that would demonstrate once and for all Jesus’ true identity. The sign that would unveil His authenticity for all the world to see is the Son of Man coming in the clouds of the sky with power and great glory (Matthew 24:30).