And the LORD said to Moses, “Thus you shall say to the people of Israel: ‘You have seen for yourselves that I have talked with you from heaven.
Moses having gone into the thick darkness, where God was, God there spoke in his hearing only, privately and without terror, all that follows hence to the end of ch. 23, which is mostly an exposition of the ten commandments; and he was to transmit it by word of mouth first, and afterwards in writing, to the people. The laws in these verses related to God's worship. I.
Commenting on Exodus 20:22-26
An altar of earth thou shall make unto me,.... This was a temporary precept, and only in force until the tabernacle was built, and respects occasional altars, erected while on their travels, and were to be made of turfs of earth, and so easily and quickly thrown up, as their case and circumstances required, and as easily thrown down, as it was proper they should...
the Lord said unto Moses--It appears from Deu 4:14-16, that this injunction was a conclusion drawn from the scene on Sinai--that as no similitude of God was displayed then, they should not attempt to make any visible figure or form of Him.