Children often play the knock, knock joke on their parents.  What if the Whos there is Jesus?   

“Behold, I stand at the door and knock. If anyone hears My voice and opens the door, I will come in to him and dine with him, and he with Me.”  Revelation 3:20

Do you hear His voice?  Many do not.  Jesus says, my sheep hear my voice.  Start off by quieting your heart and listening for the still soft voice of our Lord and savior.  Sometimes the voice is audible, but more often it is through His word, the Bible.  Hear Him today.