This sermon answers the question, "Who at the door is standing?" 1) Jesus is standing at the door. 2) The world is standing at the door. 3) You are standing at the door. Each hearer should be able to state who is standing at the door and for what reasons. To help each understand their relationship to Jesus while he stands at the door.
The basic truth of the matter is this. We either believe that people need to respond to the gospel of Jesus Christ or we do not. If we do not, then there is no use in giving an invitation. If we do, then we must make every effort with all of our heart, soul, and mind, to appeal to that person who needs to repent. We are finite humans who are limited in knowledge. We just do not know if there is someone listening who needs to respond to the gospel of Jesus. Do you want to gamble with someone’s soul by not offering them the opportunity to respond to the invitation? I sure don’t.
The invitation is that final five or ten minutes of a sermon in which the preacher invites anyone who needs to come forward to confess fault, or to become a Christian to do just that. But it is not upon the authority of the preacher—it is upon the authority of the word of God that the invitation is offered.