Matthew 5:13
"You people are [like] salt on the earth. But if salt loses its flavoring ability, how will it ever get it back again? From then on it would be good for nothing except to be thrown out onto the roadway and walked on by people. [Note: This was mined salt which, when losing its "saltiness" due to exposure to the sun or rain, was simply disposed of by being dumped onto the roadway where people walked].
Luke 14:34-35
Therefore salt is good, but if it loses its flavoring [ability], how will it ever get it back again?
Colossians 4:6
Your speech should always be favorable, seasoned with salt [i.e., interesting and appropriate], so that you may know how to properly answer each person [you talk with].
Mark 9:49-50
For everyone will be salted with fire. [Note: This meant either the suffering "salt" of fiery trials (the sacrifices of verses 43-47 or the punishing "salt" of being thrown into a fiery hell (verse 45-48)].
Hebrews 6:4-6
[These are people] who were once enlightened [by the Gospel message], who had experienced the gift from heaven [i.e., forgiveness, never ending life, etc. See Rom. 6:23], who had partaken of the Holy Spirit [See Acts 2:38],
2 Peter 2:20-21
For if people who have escaped from the defiling practices of the world by coming to know our Lord and Savior Jesus Christ, become tangled up in them again, and are overcome by them, these people are worse off than before they were converted.