Soldiers were paid their salary by receiving bags of salt. The word salary means salt. So if you are asked sometime whether you are worth your salt, you will know that someone is asking whether you are giving honest labor for the salary that you are being paid. Jesus has told us that we are the salt of the earth. Without salt, you and I would die.
Salt is a necessary seasoning that makes life on earth possible.
If we were the pepper of the earth, we would probably think we were hot stuff. But Jesus says we are the salt of the earth. Without the seasoning of salt, of love, that Christians bring to the world, the non-Christians are destined to die. We are the flavoring that makes life possible. This generally does not happen, but if it does, there is no joy in eating such food.