Based on the assumption (yes, I know it’s an assumption but I’m not going to make the case for it right now) that humans were created by God to glorify Himself in relationship with us, and the secondary assumption that God uses people to introduce other people to relationship with Him, we can conclude that the what of spreading the good news of that relationship is not something new. That said, the method and location have changed drastically since God first promised a savior to Adam and Eve, walked with Noah, and covenanted with Abraham to give him innumerable descendants, provide a land for them, and bless all the nations of the earth through him.
The method and location of the Old Testament were inextricably tied together. Canaan was the land God provided for them, and in providing it and delivering them from Egypt, He became famous. In the midst of widespread cultural understandings that gods got the glory for what happened to their people (whether that was Dagon praised for Philistine success or Yahweh recognized for delivering His people from Egypt), God showed up in ways that made His name known. He called a people for Himself and set things up so that in every aspect of daily life (see Leviticus, Numbers, and Deuteronomy), in identity (You will be my people, and I will be your God), and in reputation (for the sake of His name) the Israelites would point their neighbors and anyone else who looked at them to the one true God.
It is clear from both inside and outside the Israelite camp that God was successful, despite the failures of His people. Moses writes in Exodus 15:11-18 that the people of Philistia, Edom, and Moab were afraid because of what they had heard of God. Rahab (Joshua 2:9-11) told Joshua and Caleb that she had heard about God and understood that He was God of heaven and earth. (“Heaven and earth” indicates recognition that nowhere is outside His control, and that He reigns supreme.)
The general idea was that the character of God was demonstrated through His relationship with His people. He would bless them so that they could bless others. Psalm 67 is a great example of this. They were called to live out life showing His character then, as well. God sent out people or used the discipline of exile to spread His fame to Babylon and Assyria, among other places, but that was the exception instead of the rule.
That changed when Jesus came. Isaiah prophesied it hundreds of years earlier, speaking as a type of the Messiah:
[God] says: “It is too light a thing that you should be my servant to raise up the tribes of Jacob and to bring back the preserved of Israel; I will make you as a light for the nations, that my salvation may reach to the end of the earth.”
Obviously, Canaan’s borders didn’t go to the ends of the earth (though what was actually possessed was significantly smaller than what was promised, due to disobedience), so there had to be another plan.
**This is one part of what I spoke on at Chi Alpha tonight, and I thought I’d post some of what I learned/shared. I’ll do my best to condense and keep this to two posts.