Revelation 11:1-2 reads:
1 I was given a reed like a measuring rod and was told, “Go and measure the temple of God and the altar, with its worshipers. 2 But exclude the outer court; do not measure it, because it has been given to the Gentiles. They will trample on the holy city for 42 months. (TNIV)
ESV Study Bible:
11:1-2 John was given a measuring rod and instructed to measure the temple of God. Many dispensationalists understand this to imply that during the great tribulation the Jewish temple will be rebuilt in Jerusalem, and Jewish worship will be re-instituted there, and that it is here that, in the middle of the tribulation, the Antichrist will take “his seat in the temple of God, proclaiming himself to be God” (2 Thess. 2:4). They understand the reference to the holy city to mean literal, earthly Jerusalem. Others see the “temple” in Revelation 11 as a symbol for believers. In the OT, Ezekiel in his vision watched an angel measure the temple (Ezek. 40:2—3), but John must measure not only the sanctuary and its altar but also those who worship there. This “measuring” of persons shows both God’s protection and his ownership and suggests that the temple itself symbolizes the saints, as the NT elsewhere affirms (1 Cor. 3:16—17; Eph. 2:20—22; 1 Pet. 2:4—10; see Rev. 3:12; 21:22). John must not measure the court outside, because “the holy city” will be given over to the nations for trampling. Because this language echoes Jesus’ prediction of Jerusalem’s destruction (Luke 21:24; cf.Â Dan. 8:13), some believe that Revelation was written before A.D. 70 and predicted that disaster. Again, however, others do not think that “the holy city” (cf.Rev. 21:2; 22:19) refers to earthly Jerusalem. Instead, they understand it as a reference to the true church. They argue that 11:8 implies that the earthly Jerusalem that rejected its Messiah now belongs to “the great city,” along with Sodom and Egypt (see 17:18). Forty-two months (see also 13:5) is equivalent to “1,260 days” (counting 30 days to a month; cf. 11:3; 12:6) and “a time, times, and half a time” (3.5 years; 12:14), which is one-half of a sabbatical-year cycle, symbolizing the brevity of the church’s suffering, which lasts until Christ comes. These calculations of time echo Dan. 7:25; 12:7 and are thought by premillennialists to refer to a final “great tribulation” period (Rev. 7:14) during which the Antichrist will “make war” against the saints (13:7)
NLT Study Bible:
The similarity of Revelation 1:1-2 to Luke 21:24 is too strong to be ignored-
They will fall by the edge of the sword and be led captive into all the nations, and Jerusalem will be trampled by the Gentiles until the times of the Gentiles are fulfilled. (Luke 21:24; HCSB)
The Revelation figure depicts the earthly Jerusalem being trampled by the Romans in 70 AD, but the sparing of the true people of God (the temple, altar, and worshipers). The people of God would heed Jesus’ instructions: “So when you see the abomination of desolation, spoken of by the prophet Daniel, standing in the holy place (let the reader understand), then let those who are in Judea flee to the mountains” (Matthew 24:15-16; ESV).
The gospel parallel to Matthew 24:15-16 is Luke 21:20-21, “But when you see Jerusalem surrounded by armies, then know that its desolation has come near. Then let those who are in Judea flee to the mountains, and let those who are inside the city depart, and let not those who are out in the country enter it, for these are days of vengeance, to fulfill all that is written” (ESV)
The people of God would escape if they obeyed the words of Jesus by leaving the city when the Romans began to sweep through Judea under Vespasian and Titus. Those who ignored Jesus’ words were trampled, captured, and/or killed by the Romans in 70 AD.