Salt is a preservative. When the word is used elsewhere with reference to lands and cities, it is associated with barrenness, perpetual ruin, and inability to support human habitation (Deuteronomy 29:23; Job 39:6; Jeremiah 17:6; Zephaniah 2:9). Most likely, therefore, Abimelech in effect puts a curse on Shechem. By symbolically sowing the site with salt he consigns it to permanent desolation. It is a ritual enactment of the intense hatred he now has for the place and everything associated with it.
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45 And Abimelech fought against the city all that day. He captured the city and killed the people who were in it, and he razed the city and sowed it with salt.