Matthew 5: 13
Salt and Light

In this parable it talks about somebody being a leader and what
happens to him when he loses his leadership. Salty also refers to
being a leader in this parable for the whole human race which means
everyone, but if the leader does something bad, foolish, or wrong that
person loses his leadership no one will listen to him, trust him, or
believe in him anymore and he cannot become a leader again, because
the people don't trust or rely on him. Then when the person lost his
leadership and he's thrown out on the streets. He becomes worthless
and people ignore him and walk around him, and don't bother to give
him any respect.
I think in this parable Jesus is trying to say if you are a leader
don't be foolish otherwise people won't believe you anymore and stop
listening to you. I also think that he meant once you are a leader,
and you blow your shot there's no way of becoming a leader again
because all of the people that believed found a new leader and trust
the new one now.