John Chrysostom

When He had delivered to His Apostles such sublime precepts, so much greater than the precepts of the Law, that they might not be dismayed and say, How shall we be able to fulfil these things? He sooths their fears by mingling praises with His instructions, saying, Ye are the salt of the earth. This shews them how necessary were these precepts for them. Not for your own salvation merely, or for a single nation, but for the whole world is this doctrine committed to you. It is not for you then to flatter and deal smoothly with men, but, on the contrary, to be rough and biting as salt is. When for thus offending men by reproving them ye are reviled, rejoice; for this is the proper effect of salt to be harsh and grating to the depraved palate. Thus the evil-speaking of others will bring you no inconvenience, but will rather be a testimony of your firmness.