Through their moral qualities they were to preserve the world from moral decay. Salt is a great preservator that keeps and upholds the wholesome condition of animal life. But if the salt should lose its savor, it would be useless, except as gravel on the road, to be trodden under foot of men. Jesus uses the simile to impress upon the minds of His hearers their obligation to sustain and support the Kingdom by keeping His commandments. Savor means taste, tang, zest, property or quality.