"Not everyone who says to Me, 'Lord, Lord,' shall enter the kingdom of heaven, but he who does the will of My Father in heaven. Many will say to Me in that day, 'Lord, Lord, have we not prophesied in Your name, cast out demons in Your name, and done many wonders in Your name?' And then I will declare to them, 'I never knew you; depart from Me, you who practice lawlessness!' Matthew 7:21-23

These verses speak of the most important judgment of all. They speak of Judgment Day—the day on which everyone will be judged with finality. Note who the Judge is: Jesus.

Note also that not everyone is saved. Jesus talks about those who are not saved—specifically about the unsaved who are surprised because they were sure that they were saved. What a dreadful day that will be for this group of people!

Though the text does not explicitly say this, there is an implicit warning that we need to judge ourselves so that we will not be condemned on Judgment Day. How are we to judge ourselves?

Have we responded correctly to the gospel in faith? Are we aware that we are sinners deserving God’s wrath? Knowing that there is nothing we can do to save ourselves, and that Jesus is the only way, have we trusted in Him alone?
Since receiving Christ by faith alone, have we lived our lives seeking to follow Jesus as Lord? None of us does this perfectly, but have our lives been lived in such a way that they testify that we are in fact saved? (It is not about perfection, but direction.)

Both of these are absolutely necessary. Apart from faith in Christ, no one is saved (John 3:16, 14:6). Apart from a changed life of discipleship, there is no assurance that a person’s faith is genuine (1 John 2:3-5).

Jesus’ words in Matthew 7:21-23 underscore the fact that salvation is not by works. Those being condemned in the passage are not condemned because of a lack of good works. Those in view did good works and Jesus did not dispute that. But He called them “workers of iniquity (unrighteousness)” (KJV). Why were there religious activities deemed unrighteous? Because they were done to earn salvation (which is impossible), instead of as the result of faith in, and love for, Jesus Christ.

Judgment Day is sure and it is final. Therefore, let us examine ourselves to see that we are in the faith (2 Corinthians 13:5). And let us judge ourselves so that we will not be judged and condemned (1 Corinthians 11:31).