Yeah! Here we go!
Eph 4:32, Be kind and helpful to one another, tender-hearted [compassionate, understanding], forgiving one another [readily and freely], just as God in Christ also forgave [c]you.
Col 3:13 Forbearing one another, and forgiving one another, if any man have a quarrel against any: even as Christ forgave you, so also do ye.
Jer 31:33-34, This is the covenant I will make with the people of Israel after that time,” declares the Lord. “I will put my law in their minds and write it on their hearts. I will be their God, and they will be my people. 34 No longer will they teach their neighbor, or say to one another, ‘Know the Lord,’ because they will all know me, from the least of them to the greatest,” declares the Lord.
“For I will forgive their wickedness and will remember their sins no more.”
Hebrews 8:12, For I will be merciful to their unrighteousness, and
their sins and their iniquities will I remember no more.
Hebrews 9:11-12, But when Christ came as high priest of the good things that are now already here,[
a] he went through the greater and more perfect tabernacle that is not made with human hands, that is to say, is not a part of this creation. 12 He did not enter by means of the blood of goats and calves; but he entered the Most Holy Place once for all by
his own blood, thus obtaining[b] eternal redemption (eternally redeeming us from sins).
Hebrews 9:24-28, For Christ did not enter a sanctuary made with human hands that was only a copy of the true one; he entered heaven itself, now to appear for us in God’s presence. 25 Nor did he enter heaven to offer himself again and again, the way the high priest enters the Most Holy Place every year with blood that is not his own. 26
Otherwise Christ would have had to suffer many times since the creation of the world. But he has appeared once for all at the culmination of the ages to do away with sin by the sacrifice of himself. 27 Just as people are destined to die once, and after that to face judgment, 28
so Christ was sacrificed once to take away the sins of many; and he will appear a second time, not to bear sin, but to bring salvation to those who are waiting for him.
Hebrews 10:
The law is only a shadow of the good things that are coming—not the realities themselves. For this reason it can never, by the same sacrifices repeated endlessly year after year, make perfect those who draw near to worship. 2 Otherwise, would they not have stopped being offered? For the worshipers would have been cleansed once for all, and would no longer have felt guilty for their sins. 3 But those sacrifices are an annual reminder of sins. 4 It is impossible for the blood of bulls and goats to take away sins.
5 Therefore, when Christ came into the world, he said:
“Sacrifice and offering you did not desire,
but a body you prepared for me;
6 with burnt offerings and sin offerings
you were not pleased.
7 Then I said, ‘Here I am—it is written about me in the scroll—
I have come to do your will, my God.’”
8 First he said, “Sacrifices and offerings, burnt offerings and sin offerings you did not desire, nor were you pleased with them”—though they were offered in accordance with the law. 9 Then he said, “Here I am, I have come to do your will.” He sets aside the first to establish the second. 10 And by that will, we have been made holy through the sacrifice of the body of Jesus Christ once for all.
11 Day after day every priest stands and performs his religious duties; again and again he offers the same sacrifices, which can never take away sins. 12
But when this priest had offered for all time one sacrifice for sins, he sat down at the right hand of God, 13 and since that time he waits for his enemies to be made his footstool. 14
For by one sacrifice he has made perfect forever those who are being made holy.
15 The Holy Spirit also testifies to us about this. First he says:
16
“This is the covenant I will make with them
after that time, says the Lord.
I will put my laws in their hearts,
and I will write them on their minds.”b]">[b]
17 Then he adds:
“Their sins and lawless acts
I will remember no more.”c]">[c]
18 And where these have been forgiven, sacrifice for sin is no longer necessary.
The Verse you are referring to:
"Many will say to me on that day, ‘Lord, Lord, did we not prophesy in your name and in your name drive out demons and in your name perform many miracles?’ 23 Then I will tell them plainly, ‘I never knew you. Away from me, you evildoers!’"
Key word in here is "I never knew you," or in other words, they were never truly saved.