What was God preparing Israel for throughout the Old Testament?
Throughout the Old Testament, God was preparing the nation of Israel for a national priesthood. Israel was called to be a kingdom of priests and a holy nation, functioning as a go-between so that every Jew could lead Gentiles to a knowledge of their God.
Les explains that Israel was to be a kingdom of priests, and he defines a priest as a go-between. Since Israel already had its own priesthood, this calling was not to mediate between themselves and God, but between the Gentiles and God. Throughout the Old Testament, God was getting the nation ready for this national priesthood, where every Jew would be in a position to lead Gentiles to a knowledge of their God. At Pentecost in Acts 2, Peter continues that same frame of reference, showing that Christ came to Israel to fulfill the Old Testament promises and covenants, making a claim on the nation even after His crucifixion and resurrection.