The Bible teaches God is known by the judgment He carries out:
Psalm 9:16 The LORD is known by the judgment which he executeth:
We see that God is known by the judgment He carries out repeatedly in the Old Testament:
Exodus 14:17 And I, behold, I will harden the hearts of the Egyptians, and they shall follow them: and I will get me honour upon Pharaoh, and upon all his host, upon his chariots, and upon his horsemen.
18 And the Egyptians shall know that I am the LORD, when I have gotten me honour upon Pharaoh, upon his chariots, and upon his horsemen.
Exactly when did the Egyptians and Pharaoh 'know' that God was LORD? They knew once He destroyed them in the Red sea. No, they didn't possess knowledge at that point, they could not because they were dead and knew nothing intellectually. They knew God was LORD through the experience of being judged by Him.
Anyone can check the Old Testament to see that God often makes this statement at the point of bringing judgment on the wicked:
Ezekiel 6:7 And the slain shall fall in the midst of you, and ye shall know that I am the LORD.
Ezekiel 6:12 He that is far off shall die of the pestilence; and he that is near shall fall by the sword; and he that remaineth and is besieged shall die by the famine: thus will I accomplish my fury upon them.
13 Then shall ye know that I am the LORD, when their slain men shall be among their idols round about their altars, upon every high hill, in all the tops of the mountains, and under every green tree, and under every thick oak, the place where they did offer sweet savour to all their idols.
14 So will I stretch out my hand upon them, and make the land desolate, yea, more desolate than the wilderness toward Diblath, in all their habitations: and they shall know that I am the LORD.
Many more instances of unsaved man experiencing God's judgment followed by the statement, "and they shall know that I Am LORD" could be given.
Of course this is exactly what the New Testament is referring to when it says, "of that day and hour KNOWETH no man.” Day and hour are being used as a synonym for judgment. Therefore we can understand this to mean, that no man has yet to experience the final judgment of God. This is so because God is known by the judgment which He executeth.
What might surprise you is the fact that God also uses the phrase "and they shall know I Am LORD" when speaking of those that He saves. When addressing those that He saves the phrase is used to signify knowing God via salvation. Or, to have the experience of knowing God through the salvation He has produced within the individual. There are many examples of this, but let's start with these verses:
Ezekiel 37:5 Thus saith the Lord GOD unto these bones; Behold, I will cause breath to enter into you, and ye shall live:
6 And I will lay sinews upon you, and will bring up flesh upon you, and cover you with skin, and put breath in you, and ye shall live; and ye shall know that I am the LORD.
We know that the bringing to life of the dead dry bones points to salvation. Notice that once God breathes life into them He says, "and ye shall know that I Am LORD." Clearly indicating that He is known through the experience of salvation they are receiving.
In this beautiful chapter picturing God's magnificent salvation plan, God goes on to say:
Ezekiel 37:11 Then he said unto me, Son of man, these bones are the whole house of Israel: behold, they say, Our bones are dried, and our hope is lost: we are cut off for our parts.
12 Therefore prophesy and say unto them, Thus saith the Lord GOD; Behold, O my people, I will open your graves, and cause you to come up out of your graves, and bring you into the land of Israel.
13 And ye shall know that I am the LORD, when I have opened your graves, O my people, and brought you up out of your graves,
14 And shall put my spirit in you, and ye shall live, ...
Numerous other Scriptures can be cited that reveal this same truth. God is known in an intimate way by those that truly experience His salvation.
Since God is known by His people through the experience of salvation, we can then perfectly understand why Jesus says this:
Luke 13:25 When once the master of the house is risen up, and hath shut to the door, and ye begin to stand without, and to knock at the door, saying, Lord, Lord, open unto us; and he shall answer and say unto you, I know you not whence ye are:
26 Then shall ye begin to say, We have eaten and drunk in thy presence, and thou hast taught in our streets.
27 But he shall say, I tell you, I know you not whence ye are; depart from me, all ye workers of iniquity.
Matthew 7:21 Not every one that saith unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that doeth the will of my Father which is in heaven.
22 Many will say to me in that day, Lord, Lord, have we not prophesied in thy name? and in thy name have cast out devils? and in thy name done many wonderful works?
23 And then will I profess unto them, I never knew you: depart from me, ye that work iniquity.
I never knew you! Obviously if we know God via salvation, it also means He knows us in the same way. And so, if someone has not truly experienced the salvation of God that person is 'not known' by Christ. There's no way that this lack of 'knowing' can be intellectually in any way.
There's no doubt that Christ knew their names and every little detail about their entire lives. He simply knew them not when it came to their experience of salvation because they had never become saved.
This whole idea of 'knowing God' is very interesting. We see that God is known by the unsaved through judgment He executeth (Psalm 9:16); and that He is known by the saved through the salvation they experience.
This leads us to a very curious verse first given in the book of Jeremiah:
Jeremiah 31:33 But this shall be the covenant that I will make with the house of Israel; After those days, saith the LORD, I will put my law in their inward parts, and write it in their hearts; and will be their God, and they shall be my people.
34 And they shall teach no more every man his neighbour, and every man his brother, saying, Know the LORD: for they shall all know me, from the least of them unto the greatest of them, saith the LORD: for I will forgive their iniquity, and I will remember their sin no more.
In these verses we clearly see that God is making reference to salvation. In verse 33 the Lord speaks of putting His law (Word) in their inward parts and writing it upon their hearts. Exactly what happens when someone becomes saved. At the end of verse 34 He also says that He will 'forgive their iniquity, and I will remember their sin no more' again exactly what happens once a person experiences the grace and mercy of God in salvation.
Some, lacking understanding of what God has said here in Jeremiah 31:34 have tried to use this verse in order to say there is not to be teachers any more. "Look," they say, "it's right there plain as day for anyone to see". And next they have the person read the verse:
Jeremiah 31:34 And they shall teach no more every man his neighbour, and every man his brother, saying, Know the LORD: for they shall all know me,
"You see, there's no more teachers." It's often been pointed out to these people that they are 'teaching' that there are not to be teachers any longer and therefore violating their own doctrine.
But of course, God is not teaching in Jeremiah 31:34 that there aren't to be teachers any more. Actually, once we look carefully at what the verse is saying, if we wanted to take it literally, then we would have to say that there are not to be teachers that teach "to know the Lord" any more.
That is, it’s not saying you can't teach everything else in the Bible. Its specifically saying that "to know the Lord" is NOT to be taught.
Oh, it says, "to know the Lord.” Hey, didn't we just search the Bible and see that to know the Lord can either point to the experience of God's judgment upon you; or to the experience of His salvation?
And since Jeremiah 31:33,34 has salvation language within it, God is really saying (once we substitute “salvation” for “knowing” the LORD) that there will come a time in which there will no longer be any need for teachers to teach SALVATION because all will be SAVED.
Well, well, isn't that interesting. Once we find the spiritual meaning of 'know the Lord' we find that the teaching of Jeremiah 31:33,34 matches up perfectly with our current understanding of what God did on May 21, 2011. Basically, God's elect people have been saying this very same thing for several years now. We have been teaching (yes teaching) that we cannot teach people any longer to go to God in order to be saved (i.e., know the Lord)--why cannot we teach this? Because everyone to be saved has been saved (or as it’s put in Jeremiah no need to teach man to know the Lord "for they shall all know Me").
Since the date of May 21, 2011, anyone teaching that someone can experience salvation (know the Lord) still, is violating the Scriptures and teaching the one thing that God prohibits from being taught in the Day of Judgment.
One last thing, those that oppose the idea of the Lord shutting the door of heaven, often try to make the doctrine sound hateful and unloving as possible, while painting themselves as dear compassionate and loving souls that would never do that to their fellow man (as if God's salvation was something they controlled and were in charge of bestowing or holding back)---and yet the true reason that God has shut the door of heaven is due to the simple fact that He chose a people for Himself and has finally, after many thousands of years of gathering them found and saved them all. They all now know the LORD. This is not an ugly thing that is to be abhorred.
The fact that God has completed His magnificent salvation program is a truly glorious thing that
the people of God ought to praise Him and constantly thank Him for doing. It also signals to us that just as God was faithful to complete the salvation of the soul He will soon complete the overall salvation of His people by saving their physical bodies through the resurrection.