What does Jesus promise to those who heed his knock and open the door?
A travelling salesman knocks on a door hoping to be invited in to discuss his product. That may happen best around a meal (or a coffee). Jesus promises to accept an invitation to sit at table with those who open the door.
20 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.