luke 21:28 And when these things begin to come to pass, then look up, and lift up your heads; for your redemption draweth nigh. - Free Bible Online

      28. redemption--from the oppression of ecclesiastical despotism and legal bondage by the total subversion of the Jewish state and the firm establishment of the evangelical kingdom (Lu 21:31). But the words are of far wider and more precious import. Matthew (Mt 24:30) says, "And then shall appear the sign of the Son of man in heaven," evidently something distinct from Himself, mentioned immediately after. What this was intended to mean, interpreters are not agreed. But as before Christ came to destroy Jerusalem, some appalling portents were seen in the air, so before His personal appearing it is likely that something analogous will be witnessed, though of what nature it is vain to conjecture.

JFB.