Everyone will be salted with fire, Mark 9:49

Jesus Christ begins his teachings with the sermon of the mountain, with the beatitudes (Matthew 5:3-12 and Luke 6: 20-23), the beatitudes are promises, perfections, excellencies and respond to the desire for the good (wisdom).
Some of these promises are very specific: "Blessed are the pure in heart, for they shall see God" (Matthew 5: 8). What does it mean to see God? In eternal life: This is the eternal life, that they may know you the only true God. John 17: 3.
After the teaching of the beatitudes, there is a dialogue between Christ and his disciples: "Jesus said to Simon Peter: Simon, son of John, do you Agape me more than these? Yes, Lord, you know that I Philia you", John 21: 15-16
This is a dialogue between two levels of love, one "Agape", the spiritual love, the love projected towards to all the work of God; in the other hand "Philia", the love that is born of the pleasure of seeing us reflected in the others, the love of friendship.
After this dialogue Christ promises them the holy spirit, promises the Gnosis:
"Everyone will be salted with fire" Mark 9:49
The salt symbolizes the wisdom of god, the fire the energy of god. This promise will be realized in Pentecost: Acts of the Apostles 2
http://www.quintoevangelio.com.ar/en/articles/item/49-gnosis.html