From Matthew 24:
30 “Then will appear the sign of the Son of Man in heaven. And then all the peoples of the earth will mourn when they see the Son of Man coming on the clouds of heaven, with power and great glory. 31 And he will send his angels with a loud trumpet call, and they will gather his elect from the four winds, from one end of the heavens to the other.
32 “Now learn this lesson from the fig tree: As soon as its twigs get tender and its leaves come out, you know that summer is near. 33 Even so, when you see all these things, you know that it is near, right at the door. 34 Truly I tell you, this generation will certainly not pass away until all these things have happened. 35 Heaven and earth will pass away, but my words will never pass away.