Mark 8:36
For what does it profit a man, to gain the whole world, and forfeit his life?
WEB
For what shall it profit a man, if he shall gain the whole world, and lose his own soul?
KJV
What Mark 8:36 means
In the middle of teaching that following him means self-denial, Jesus asks what good it is to gain the whole world while losing your own soul, weighing every possible profit against the one thing that can't be bought back.
Mark 8:36 falls at a hinge in Mark's Gospel. Jesus has just begun telling his followers that he will suffer and die, and that anyone who wants to follow him must "take up their cross." Against that, he poses a blunt cost-benefit question: what does it profit a person to gain the whole world and forfeit their soul?
The image would have stung in any age, but especially one without safety nets, where survival pressed hard and gaining "the world" meant security itself. Jesus does not say the world is worthless. He says there is an exchange rate, and that a person can win everything outside and lose the very self that was supposed to enjoy it. He follows it with a second question: what would a person give in return for their soul? The implied answer is that some things, once traded away, cannot be bought back at any price.
The word the translation renders "soul" is the Greek psyche, which also means "life" or "self," which is why some translations read "forfeit his life" and others "his soul." It is not only the religious soul of the afterlife; it is the living center of a person, the you that the whole pursuit was for. That doubled meaning is the point: lose that, and whatever you gained is held by no one.