Let your speech be alway with grace, seasoned with salt, that ye may know how ye ought to answer every man. Colossians 4:6
Picturing a man salting his tongue is thinking like a Westerner—not an Easterner! In our culture, 'salty' speech is associated with pirates and risque behavior. This isn't talking about taste, but about something entirely different.
In Leviticus 2:13, God told Israel to season with salt all their offerings. In the East, salt represented, among other things, a sacred covenant. This "covenant of salt" bound people together, even unto death. Our words are to be salted because when we speak as people of the covenant, we represent our Father's word! We are to be true, not only have truth. The power of the 'salt covenant' also represents peace and harmony between the saints.
Just as salt acts as a preservative, we as 'salty saints' can be a very great blessing wherever we are, and may be the reason that an area is spared in times of the Lord's wrath.
For other verses on the Covenant of Salt see also Numbers 18:19 and II Chronicles 13:5.