The New International Version states it like this - "Here I am! I stand at the door and knock. If anyone hears my voice and opens the door, I will come in and eat with him, and he with me."
The Biblical address is Revelation 3:20. I have seen this verse on paintings and used in teaching/preachings as invitations to unbelievers. If you read carefully before and after this verse - in other words, read this verse in context - you will observe this was spoken to Believers. Thus, this is my main challenge to you in this writing today - when reading the Scriptures Consider the Context!
Allow me to demonstrate my meaning. Let us take a look at Revelation 3:20 and it's surrounding verses.
To the Church in Laodicea
14 "To the angel of the church in Laodicea write: These are the words of the Amen, the faithful and true witness, the ruler of God's creation. 15 I know your deeds, that you are neither cold nor hot. I wish you were either one or the other! 16 So, because you are lukewarm--neither hot nor cold--I am about to spit you out of my mouth. 17 You say, 'I am rich; I have acquired wealth and do not need a thing.' But you do not realize that you are wretched, pitiful, poor, blind and naked. 18 I counsel you to buy from me gold refined in the fire, so you can become rich; and white clothes to wear, so you can cover your shameful nakedness; and salve to put on your eyes, so you can see.19 Those whom I love I rebuke and discipline. So be earnest, and repent. 20 Here I am! I stand at the door and knock. If anyone hears my voice and opens the door, I will come in and eat with him, and he with me. 21 To him who overcomes, I will give the right to sit with me on my throne, just as I overcame and sat down with my Father on his throne. 22 He who has an ear, let him hear what the Spirit says to the churches."
This verse falls in a section of verses from 14-22 that deals with The Church of Laodicea. The Lord is addressing Believers, The Church, at Laodicea. The Lord does not concern His remarks with Salvation because these people are already "saved".
Jesus begins with these Believers by saying, "I know your deeds,". Their disgusting service ("deeds") for God ("neither hot nor cold") and their dependence on their wealth were such terrible faults that Jesus labeled them "wretched, pitiful, poor, blind, and naked". He also says, in the body of this address - "Those whom I love I rebuke and discipline. So be earnest, and repent." (v.19) Again, these are verses that support these people, and possibly in particular the leadership of the church ("To the angel of the church in Laodicea write:"), having already received the Good News of Jesus Christ into their lives, they just need to turn their actions around 180 degrees toward God ("repent").
The imagery of Jesus at the door knocking and if anyone hears His voice and opens the door I will come in and eat with him and he with me - is an image meant to place Jesus back where He belongs, Off Of The Front Porch And In Your House/Temple! The Believers of Laodicea had replaced their reliance on God with "lukewarm" deeds and dependence on self-wealth. This puts Jesus out in the cold. Therefore, you have a loving, rebuking, disciplining Savior who now stands at the door to your life and knocks for re-entry. Not necessarily re-entry as a re-dedication of your heart concerning salvation, remember you and these people are Believers, but a re-dedication of your priorities and services for The King - your deeds. Context.