“You are the salt of the earth . . but if the salt loses it’s saltiness . . . .”. Jesus says we are the people who should have a great positive influence on those we meet during any week – just like salt which flavours and preserves it’s surroundings.
It sounds a bit of a contradiction to say “if the salt loses it’s saltiness .  . .” because there would be nothing left! But the image is one of sea foam where the salt has been leached out and we’re just left with ‘mush’!! Today we think of how we can be effective – like salt – for God.