16:14 hardness of heart. The Greek word for “hardness of heart” is sklerokardia, from which is derived our English word “cardiosclerosis.” There are some forty references in the Bible to what may be called spiritual cardiosclerosis, the first in connection with Pharaoh’s hardness of heart (Exodus 4:21). We are warned: “To day if ye will hear his voice, harden not your hearts” (Hebrews 4:7), in the final such reference.