"Not everyone who says to me, 'Lord, Lord,' will enter the kingdom of heaven, but only the one who does the will of my Father in heaven. Many will say to me on that day, 'Lord, Lord, did we not prophesy in your name? Did we not drive out demons in your name? Did we not do mighty deeds in your name?' Then I will declare to them solemnly, 'I never knew you. Depart from me, you evildoers.'--Matthew 7:21-23Most people take this passage to mean some people were never saved, even though they may have been perceived to be, or they themselves may have mistook themselves to be such. I have encountered believers in Once Saved Always Saved (OSAS) who used this verse to 'support' their position some odd way. Others I have met said these people were boasting about their own works before God and were damned or were never saved because they did so.
So, does "never knew you" mean he never really know them, hence they were never saved? Not necessarily. This is because it is quite possible Jesus was using an Rabbinical expression. This is noted by Samuel Tobias Lachs in his A rabbinic commentary on the New Testament, who on page 150 of his book notes that "never knew you" is "An expression of rejection used by the Rabbis, often as a form of a ban," then cites instances in Talmudic literature, such as MQ 16a (Mo'ed Katan), which has a story about a rabbi that told a person he knew that "I have never known thee." In addition, St Cyril of Alexandria commenting on Matthew 7:21-23 says:
"There may be some who, in the beginning, believed rightly and assiduously labored at virtue. They may have even worked miracles and prophesied and cast out demons. And yet later they are found turning aside to evil, to self assertive deception and desire. Of these Jesus remarks that he "never knew them." He ranks them as equivalent to those who were never knew by him at all...."--St Cyril of Alexandria, fragment 88It should also be noted that Prophecy does not even necessarily show proof of salvation since the High Priest that sought the death of Christ in John 11 seems to speak prophecy, and 1 Corinthians 13 says:
And if I have the gift of prophecy and comprehend all mysteries and all knowledge; if I have all faith so as to move mountains but do not have love, I am nothing.-1 Corinthians 13:2Now, some claim these people are bragging about their works, so they cannot be saved. However, look closely, they are not!
Lord, Lord, did we not prophesy in your name? Did we not drive out demons in your name? Did we not do mighty deeds in your name?'These people are attributing these deeds to GOD, not themselves!
Some will claim these are just false prophets, it could be they became false prophets, however, consider this, can a person fake casting out demons? Jesus accused the Pharisees of blaspheme for saying God is not the one that casts out the demons.
Conclusion: Though there are verses that certainly teach there are false converts, Matthew 7:21-23 is not likely one of them.