Luke 14:27 KJV
And whosoever doth not bear his cross, and come after me, cannot be my disciple.
The Bibles says that there were great multitudes following Jesus when He turned to them and, in words that had to have been taken sternly, gave them a threefold test of discipleship;
The test of devotion.
The disciple must love the Lord above all else. Family and friends cannot be first for the disciple.
The test of witness.
The English word for witness is the same as martyr. The earliest form of witness was martyrdom. The disciple must testify for Christ.
The test of perseverance.
There is no turning back in discipleship.
The would be disciple who fails the test is like salt that has lost its savor and is good for nothing.
Salt can't lose its saltiness. So a true disciple cannot fail the test. To fail merely proves the one was never a true disciple.