Exodus 19 - Israel now arrives at Mt. Sinai and will spend approximately two years there. God calls Moses up to the mountain to prepare to receive God's law for Israel to follow. Moses goes back to the camp to purify the people and warn them not to approach the mount. God wants to instill within them a healthy fear in their hearts towards Him.
Exodus 20 - God gives the Ten Commandments which focus on Israel's relationship with Him in the first four commandments, and then their relationship with each other in the last six. Commandment number five, the matter of honoring parents, is pivotal. Parents have the responsibility of showing their children how to obey the first four commandments that relate God and the last five commandments that relate to their fellowman. The people ask Moses to be the one to listen to God and tell them what He says. God teaches Moses how to build an altar for worship.
Exodus 21 - God gives laws regarding the proper treatment of servants in light of the prevailing attitudes of that day. The death penalty for murder is repeated here and the first thought that would lead to the cities of refuge is mentioned.