Luke 21:26-28

Luke 21:26-28

[26] Men's  hearts failing them  for  fear,  and  for looking after  those things which are coming on  the earth:  for  the powers  of heaven  shall be shaken.  [27] And  then  the Son  of man  coming  in  a cloud  with  power  and  great  glory.  [28] And  begin  to come to pass,  then look up,  and  lift up  heads;  for  redemption  draweth nigh. 

What is the context of Luke 21:26-28?