Question: "What is the significance of the command to flee to the mountains (Matthew 24:16; Mark 13:3; Luke 21:21)?"
Answer: Mark 13 records what is often referred to as Jesus’ Olivet Discourse (also recorded in Matthew 24 and Luke 21). At this time, Jesus and His disciples are on the Mount of Olives, or Mount Olivet, and the Lord addresses the disciples’ questions (Mark 13:3–4) about the future. Jesus warns His listeners that one day people in Judea will need to flee to the mountains (Mark 13:14).
Just before the Olivet Discourse, as Jesus and His disciples were leaving the temple, the disciples were marveling about the architecture (Mark 13:1). Jesus remarked that the buildings they were admiring would all be destroyed one day (Mark 13:2), and the disciples began asking when these things would take place and when all would be fulfilled (Mark 13:3–4). On Mt. Olivet, Jesus explained that there would be wars and rumors of wars, but these would be merely birth pangs (Mark 13:5–8). Before the time of the end, the disciples would be persecuted and stand trial as a testimony (Mark 13:9), as the good news of Jesus needed to be proclaimed in all the nations (Mark 13:10). The Holy Spirit would give the disciples the words to say when they faced these situations (Mark 13:11). And, eventually, there would come difficult times when people would need to flee to the mountains (Mark 13:14).
Prior to the fulfilling of the end of the age (as Matthew records in Matthew 24:3), a great division will occur (Mark 13:12), many will fall away, false prophets will arise, lawlessness will increase (Matthew 24:10–11), and the disciples would be hated because of Jesus (Mark 13:13). But the one who endures to the end will be delivered through those difficult days (Mark 13:13). Though those days are survivable, Jesus warns that there will come a time of greater severity when, in order to survive at all, one must flee to the mountains (Mark 13:14). When people see the abomination of desolation, then those in Judea must flee to the mountains (Mark 13:14).
The mention of the abomination of desolation is a reference to Daniel 9:27. There, the angel Gabriel explains to Daniel that, at the midpoint of a seven-year period, a person associated with abominations and who makes things desolate will do something awful in the temple. Mark 13:14 refers to that person “standing where he ought not to be” (ESV), that is, in the temple. When that takes place, Jesus says, the situation will get so severe that the people of Judea (not just Jerusalem) must flee to the mountains to escape. They must do so hurriedly (Mark 13:15–16), apparently because of the suddenness of the calamity that will come. Jesus explains that at that time there would be tribulation and distress “unequaled from the beginning, when God created the world, until now—and never to be equaled again” (Mark 13:19). The people who will see those events will need to flee to the mountains of Judea in order to survive, but Jesus reminds His listeners to take heed because He has told them these things in advance (Mark 13:23).
It is common for prophecies to be given far in advance for the benefit of the people of that present day. Even though the events may not take place for many years, the knowledge of how things will unfold should encourage, challenge, and motivate the hearers of the prophecy. As we read the prophecy and know that one day things will be so severe that people will have to flee to the mountains, we should make the most of the time we are given and be thankful that we are not seeing such severity constantly in our time.