And if thou wilt make me an altar of stone, thou shalt not build it of hewn stone: for if thou lift up thy tool upon it, thou hast polluted it.
God spoke to you from heaven itself, not as some prince condescending to beggars, yet you turn to silver and gold images as if He were absent or unknown. This is the sin He means to crush: you have seen no form, heard only His voice, and that very silence about His shape forbids you to make one. Keep communion with God by His word, not by idols.
AI summary
Commenting on Exodus 20:22-26
thou shalt not build it of hewn stone, &c.--that is, carved with figures and ornaments that might lead to superstition.
Thou shalt not build it of hewn stone - Because they were now in a wandering state, and had as yet no fixed residence; and therefore no time should be wasted to rear costly altars, which could not be transported with them, and which they must soon leave.