The Sermon on the Mount winds up on a note that emphatically lacks the fragrance of the Protestant sola fide doctrine:
Not every one who says to me, ‘Lord, Lord,’ shall enter the kingdom of heaven, but he who does the will of my Father who is in heaven. On that day many will say to me, ‘Lord, Lord, did we not prophesy in your name, and cast out demons in your name, and do many mighty works in your name?’ And then will I declare to them, ‘I never knew you; depart from me, you evildoers.’ (Matthew 7:21-23, RSV2CE)
If we are actually justified by faith alone as we are told, then Lord, Lord ought by rights to be all that is necessary to open the gates of heaven. Jesus says otherwise here (and in the parable of the sheep and the goats). Please note that the people referred to here didn’t just prophesy in His name, but also cast demons out. The only record we have of an unbeliever attempting this does not end well, yet these people say they did cast out demons. It seems difficult to imagine, then, that they were not genuine Christians.
And they lost their salvation.
This should not be surprising to us. We have seen it recently in Ezekiel too. What we Christians do matters. If we live lives of disobedience toward God, Jesus may indeed say to us, “I never knew you.”