18 And all the people saw the thunderings, and the lightnings, and the noise of the trumpet, and the mountain smoking. And when the people saw it, they backed up and stood far off.
19 And they said to Moses, “Speak thou with us, and we will hear, but don't let God speak with us, or we'll die!”
It was God's intention to bring the people up to the mountain to have a personal relationship with Him. The people chose to be too afraid to do this and told Moses they would rather have him as an intermediary.
20 And Moses said to the people, “Don't be afraid, because God is come to test you so that the fear of Him will keep you from sinning.”
21 And the people stood far away, and Moses drew near to the thick darkness where God was.
22 And the I AM said to Moses, “This is what thou shall say to the children of Israel, ‘Ye have seen that I have talked with you from heaven.’”
God agreed to their decision.
23 Ye shall not make with other gods of silver and gold to worship along with Me.
24 An altar of earth thou shall make to Me, and shall sacrifice on it thy burnt offerings, and thy peace offerings, thy sheep, and thine oxen, in all places where My name is remembered I will come to thee, and I will bless thee.
25 And if thou will make Me an altar of stone, thou will not build it of carved stone. For if thou use a tool on it, thou have polluted it.
God did not want them to do any carving at all in worshiping Him. This would distract from paying attention to Him.
26 Neither shall thou go up by steps to My altar, that thy nakedness be not seen on it.
Pagans often climbed steps up to their alters. Since pants are too hard to weave unless necessary, and aren't necessary unless you are riding a horse, a priest's private parts could easily be visible in such a climb. This certainly would distract from concentrating on God!