If we listen very carefully, we can hear a "knocking" sound. Do you hear it? "Knock, knock, knock." And we all know what to do when we hear that sound: We go to the door to find out who is there. When Jesus says that He stands at the door, and is knocking, He is telling us that He is trying to get our attention. He is trying to let us know that He is there.
Jesus at the door
Behold, I stand at the door and knock. If anyone hears my voice and opens the door, I will come in to him and eat with him, and he with me.
Be like men waiting for their master to return from the wedding feast, ready to open the door as soon as he comes and knocks. ... from a wedding feast may be coming back with some take home gifts and other good and pleasant things.
I can hear a "knocking" sound. Do you hear it? "Knock, knock, knock."