When Matthew quotes Jesus using the phrase “never knew you” in Matt 7:21 the Greek word for never is Strong’s #3763.
Matthew uses the same word when He cites Jesus’ statement asking the Scribes etc. have you never read… in Mt 21:16 and Mt 21:42.
Mt 21:16 And said unto him, Hearest thou what these say? And Jesus saith unto them, Yea; have ye never (3763) read, Out of the mouth of babes and sucklings thou hast perfected praise?
Mt 21:42 Jesus saith unto them, Did ye never (3763) read in the scriptures, The stone which the builders rejected, the same has become the head of the corner: this is the Lord’s doing, and it is marvelous in our eyes?
The experts in the Law had most certainly read these verses before, and this suggests that Jesus was using the word “never” to draw their attention to truths that they had not applied to that situation.
In turn, it also suggests that when Matthew uses the same word in Mt 7:21 the translation is not exact and that He is not saying that Jesus never knew them at any point in their lives.
It may not imply that Jesus “Never” knew the people who called Him Lord, but instead that they were not obedient at that time.
The translation of the Greek in Luke 13:25 is more accurate in this situation than that of Matt 7:21 since it does not convey the idea of “never having known people who call Him Lord”. Instead, it conveys the idea of Jesus not recognizing where they come from.
We know that Jesus will not reject anyone who comes to Him, Jn 6:37.
John 6:37 All that the Father giveth me shall come to me, and him that cometh to me I will in no wise cast out.
Lu 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:
Lu 13:27 But he shall say, I tell you, I know you not whence ye are; depart from me, all ye workers of iniquity.
A Christian can be sent into the presence of the Devil and his angels (Hell) and they can come out upon repentance from the activity that prompted Jesus to send them there as Matt 5:26 and Luke 12:59 illustrate.
Just as God used Satan to discipline Job, Jesus used the devil in this situation and Paul used it in 1 Cor 5:5.
1Co 5:5 To deliver such a one unto Satan for the destruction of the flesh, that the spirit may be saved in the day of the Lord Jesus.
Jesus is not telling people who call him Lord that He never knew them at any time and that they would not be saved, He is sending them to Hell for correction.
As we can see from Matt 25:23 some people enter the kingdom (righteousness joy and peace) to a greater degree and some go into the fire, and are saved through the fire, 1 Cor 3:15.
Mt 25:23 His lord said unto him, Well done, good and faithful servant; thou hast been faithful over a few things, I will make thee ruler over many things: enter thou into the joy of thy lord.
1Co 3:15 If any man’s work shall be burned, he shall suffer loss: but he himself shall be saved; yet so as by fire.
Jesus refused to allow some people who called him Lord into the kingdom of God in Matt 25:41, and yet He also said I will reject no one who comes to me in John 6:37.
Jesus did not allow these Christians to enter the kingdom of righteousness joy and peace in the Holy Spirit because they had not been taught to deny ungodliness yet.
Mt 25:41 Then shall he say also unto them on the left hand, Depart from me, ye cursed, into everlasting fire, prepared for the devil and his angels:
Mt 5:26 Verily I say unto thee, Thou shalt by no means come out thence, till thou hast paid the uttermost farthing.
Lu 12:59 I tell thee, thou shalt not depart thence, till thou hast paid the very last mite.