Matthew 24:21-22, 29-31

for then shall be great tribulation, such as hath not been from the beginning of the world until now, no, nor ever shall be. And except those days had been shortened, no flesh would have been saved: but for the elect’s sake those days shall be shortened.

But immediately after the tribulation of those days the sun shall be darkened, and the moon shall not give her light, and the stars shall fall from heaven, and the powers of the heavens shall be shaken: and then shall appear the sign of the Son of man in heaven: and then shall all the tribes of the earth mourn, and they shall see the Son of man coming on the clouds of heaven with power and great glory. And he shall send forth his angels with a great sound of a trumpet, and they shall gather together his elect from the four winds, from one end of heaven to the other.