Exodus 20:25

25. If thou wilt make me an altar of stone Such an altar would be as simple and easy of construction as one of turf, and more so in places where stones abounded . But to preserve its simplicity, and to deter from attempts to imitate the sculptured embellishments of heathen altars, they were forbidden to make use of hewn stone, or to wield a graver’s tool upon it . The natural stone, untouched by art or man’s device, was most like the earth itself, and most appropriate for the sanctity and simplicity of the altar-service . Any attempt to cut or carve the stones would be a polluting of holy things . The framework of acacia wood, overlaid with brass, was a subsequent and special provision for the altar of the tabernacle . See Exodus 27:1-8.