(a) In the Wilderness of Sin, the people of Israel encamped at the mountain as instructed by God. Moses went up the mountain to hear what God had to tell him. He was to address the people so that they would appreciate what God did for them when they were in Egypt, especially how He bore them on eagle's wings. They should obey God and keep His laws. God said that they shall be His own possession, they shall be a holy nation. Moses delivered God's message to the people. They promised to obey all that the Lord had spoken to them as delivered by Moses. Moses went back to God and reported the people's response. The Lord said he would return to them in a thick cloud so that they might hear Him speak to Moses and believe that it was Him that spoke. God instructed Moses to go and consecrate them. He also warned that there must be a distance between the people and God for anybody who goes near the Lord would be destroyed.

(b) The preparation became necessary because
(i) God is holy.
(ii) No body should disobey Him; any disobedience would be punished by God.
(iii) Due to the holiness of God, whoever approaches the mountain to hear God must himself be holy.