Moses went up to God, and the LORD called to him from the mountain, saying, “Thus you shall say to the house of Jacob and tell the sons of Israel: ‘You yourselves have seen what I did to the Egyptians, and [how] I bore you on eagles’ wings, and brought you to Myself. ‘Now then, if you will indeed obey My voice and keep My covenant, then you shall be My own possession among all the peoples, for all the earth is Mine; and you shall be to Me a kingdom of priests and a holy nation.’ These are the words that you shall speak to the sons of Israel.”
Exodus 19:3-6
This is the first mention in the Bible of a physical, identifiable kingdom related to God’s purpose and will among men. At Sinai, God was setting apart a people for himself. The Kingdom would become a theme and pattern woven throughout the rest of the biblical narrative.
The Core of the Bible 