Ecclesiastes 1:34-36

34 Verily, I say unto you, this generation, in which these things shall be shown forth, shall not pass away until all I have told you shall be fulfilled.

35 Although, the days will come, that heaven and earth shall pass away; yet my words shall not pass away, but all shall be fulfilled.

36 And, as I said before, after the tribulation of those days, and the powers of the heavens shall be shaken, 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 in the clouds of heaven, with power and great glory;