Exodus 24

2 The elders were to be a special witness of Moses' relationship with God.
4 Here we see a combination of an altar to God and a memorial to Israel. The symbolism appears to be that the twelve tribes were to constantly worship God. The focal point was the altar where atonement for sin was to take place.
5 You are never too young to serve God. Parents need to make a special effort to get their children involved in church life. Some parents stay outside or on the margin of church life and want to let their children "decide for themselves." One problem with this is that the children grow up outside the church. They see church as dull and boring because they are never involved. They may also miss out not only on hearing the Good News of Jesus, but on seeing how the Christian life is lived out (that is, if the parents have not taken on this responsibility themselves, as they should have).
6 Sprinkling blood on the altar was done to purify it and to sanctify it for the purpose of making sacrifices and offerings to God. Not only must the sacrifice be unblemished, but the method of sacrifice must be purified as well. In other words, we must worship the way God desires us to worship Him.
7 It is not enough just to go to church and read or hear the word of God. One must also agree with it and then be obedient to God's commands. Living out a godly life is much more difficult than acknowledging that it should be done.
8 The blood was sprinkled on the people. This was a dramatic symbol of how sin was atoned fore. The perfect and innocent sacrifice gave up its life, and its blood was used to atone for the sins of those who were neither perfect nor innocent. This is a striking parallel to what Jesus did on the cross for us. When one sings songs referring to the "blood of the lamb" or to the "blood of Jesus" this is exactly the picture that should come to mind.

Yes, it is a grizzly scene, but that is how God sees our sin. Sin must be paid for, and the only acceptable price is a perfect life to be substituted for a sinful life (Lev 17:11, Rom 5:8, 9, Heb 10:9-22).

10 The elders were given special evidence that Moses was communicating with God. They did not have to view the fiery mountain from a distance, nor did they have to wonder where the voice came from. God graciously reveals Himself to them.

There is a question, though, about what the men really saw. Several verses indicate that no one has really "seen" God because of His spiritual nature and because of our sin (Judg 13:22, John 1:18, Exo 33:18-23). We only really know that the men saw His feet. The rest of the theophany may have been covered in a bright cloud or a dazzling garment that obscured God's face (Mat 17:2-5).

11 To share a meal with someone was an indication of hospitality and friendship. God wants to have a personal relationship with each one of us and promises to accept any invitation (Rev 3:20).
12 Notice that here God makes the stone tablets and writes on them. He is able to communicate directly to people, but once the commands are given to the leadership they are expected to teach the followers. From the very beginning God has given man the honor and responsibility of working with and for God.
13 Moses was not a super-human or a perfect man. He required a close personal assistant (and several others) to help him carry out the mission that God called him to. Being an assistant is not a bad thing. While the assistant is not in charge, he learns important skills directly from the leader. When Moses dies, Joshua is the one who is given command over the armies of Israel. He was close to God and had the best training possible from Moses.
14 Here we get an early picture of the dual rulership of Israel. The representatives from the high priesthood (Aaron) and the eventual ruling tribe (Judah) are appointed to lead Israel and resolve any disputes that arise in Moses' absence. This dual leadership is reestablished at the coronation of David as king. Later this dual role of spiritual and physical kingship would be merged in Jesus.
16 God called Moses, but he was not to come immediately. For six days Moses was to prepare himself to stand in the presence of God's theophany. Finally, when the time was right, God calls Moses to approach closer.

In our own lives God calls each one of us into His presence, but we can not just rush right in. Approaching God involves prayer and meditation. This does not mean we have to become perfect to approach God, nor does it mean He will not meet us where we are, but when the heart and mind are focused on God, He can most easily speak to us, and we are most likely to listen.

17 We don't really know what this looked like, but the closest thing the Israelites could relate the appearance to was fire.
18 But what the theophany looked like was not important. The fact that God was present was important.

Even though Moses prepared for six days before he went up the mountain, God had him wait another 40 days before He spoke.