Exodus 19:1-25

"Then Moses climbed the mountain to appear before God. The LORD called to him from the mountain and said, “Give these instructions to the family of Jacob; announce it to the descendants of Israel: ‘You have seen what I did to the Egyptians. You know how I carried you on eagles’ wings and brought you to myself. Now if you will obey me and keep my covenant, you will be my own special treasure from among all the peoples on earth; for all the earth belongs to me. And you will be my kingdom of priests, my holy nation.’ This is the message you must give to the people of Israel.” v3-6
God had a reason for rescuing the Israelites from slavery. How he was ready to tell them what it was: Israel was to become a kingdom of priest and a holy nation where anyone could approach God freely. It didn't take long, however, for the people to corrupt God's plan. God then established Aaron's descendants from the tribe of Levi as priest representing what the entire nation should have been. But with the coming of Jesus Christ, God has once again extended his plan to all believers. We are to become holy, "royal priest". The death and resurrection of of Christ has allowed each of us to approach God freely.

Taken from the NLT Life Application Study Bible