What is the relationship between the Great Commission and the Old Covenant? This is a big topic, and so I will limit myself to one passage: Genesis 12. There are at least three missiological principles to consider, which we will approach in the form of a catechism.
Question 1: Is missiology only a New Testament idea?
Answer: Missiology spans both testaments.
“In you all the families of the earth will be blessed” (Genesis 12:3). God promised to bless the earth through Abraham. Paul told the Galatians (3:8) that this Abrahamic promise is the Gospel, the blessing itself taking effect “in Christ Jesus” (v.14). God’s promise to Abraham was nothing short of the innumerable throng gathered around the throne (Revelation 7). Abraham, childless in the desert, is promised the families of the earth as an inheritance. Also, this helps us define “missions,” which can be misleading. There is only one mission. “Missions” is our participation in the salvation of the world.
Question 2: If God has always meant to bless the nations, then why did he wait to issue the Great Commission?
Answer: The Great Commission is a strictly New Covenant venture because only in the New Covenant is Jesus Lord and his Gospel explicit.
The blessing of Genesis 12:3 is evangelical, top to bottom, but the mechanics of that blessing are hidden. In the Old Covenant, God saved his people by grace through faith, but that doesn’t necessitate an explicit gospel. After all, it is not “the gospel” that saves or in which men are to put their faith. God saves; it is his gospel. “Abraham believed the Lord, and it was counted to him as righteousness” (15:6).
We did not learn the gospel in detail until Christ was born, died, and rose again. In fact, historically speaking, the life, death, resurrection, and reign of Christ is the gospel. The gospel is that he reigns and his kingdom has come. As the Old Covenant waned, having waxed full, promises of a Harbinger of Abraham’s promise became clearer and clearer. A Messiah would come. The gospel of Jesus Christ existed in the Old Covenant, but it was in a veiled, promissary form – though perfect, complete, assured, and explicit in the mind of God (Acts 4:28).
How could the church baptize and instruct the nations if Christ has not come? Baptizing and teaching are the particulars of the Great Commission, after all. Was Elijah to baptize the nations into Christ, demanding their allegiance to a King who had not ascended? Was Joshua to teach Israel the words of Christ? These questions are nonsensical, because the Messiah had not come. There can be no missions without the person and work of Christ. Old Testament missiology cannot move beyond this fact.
As should be expected, there are no examples of Great Commission work being done under the Old Covenant. Not even with Jonah, who preached judgment, not grace through Christ (Jonah 3:1-10). Nineveh repented and believed the word of God concerning that judgment. The story of Jonah is not an example of the Great Commission in the Old Testament, but it does seem to be a foretaste of it. What happened in Nineveh is a picture of what God would one day do among all nations in Christ.
Examples like Jonah/Nineveh clarify what we have already stated, but also compel us to go further. The Great Commission is an inappropriate standard to hold the Old Covenant to, but it remains a fitting paradigm to see the Old Covenant fit into. The Old Testament clearly has missiological themes and threads. A problem arises when we seek to equate and over-simplify the idea of “missions” in Scripture, as though it were the same thing from beginning to end. Genesis to Revelation, God has the same, unchanging, sovereignly administered plan of spreading his Kingdom, his garden, across the face of the earth. The New Covenant billows onward with the Great Commission, and the Old Covenant foreshadows and prepares the way for that mission. Old Testament missiology is the forerunner to New Testament missiology, in a remarkably similar way to how Old Testament Israel is the forerunner to the New Testament church. And, running off this comparison, they are one in the same, only different according to the age in which they reside.
Question 3: Why did God wait so long to bring about the incarnation, the explicit gospel, and the salvation of the nations?
Answer: God waited as long as he did because he wanted to, because missions is unnecessary.
By “unnecessary,” we certainly are not referring to God’s plan to glorify himself in the redemption of sinners, or to man’s depravity and need of redemption, or to the global scope of the promise given to Abraham. By “unnecessary,” we mean the base existence of missions. God is not obligated, by anything other than his Word, to bless the nations in Christ. Missions does not have to exist.
The context of Genesis 12:1-3 supports this point. The preceding paragraph (11:10-32) records a genealogy from Shem to Abraham. The promises made to Abraham were merciful and glorious, but why did God not give them to Terah, Abraham’s father? Or Nahor before him? What of Serug, Reu, Peleg, Eber, Shelah, or Arpachshad? The answer is that God freely chose to bless Abraham in this way, and He was not obligated to do so to anyone.
Even earlier in Genesis rests perhaps the best example of how God doesn’t have to bless the nations (6:9-9:17). The Flood was God’s judgment of the world for wickedness. The families of the earth were disobedient. Instead of giving Noah a Great Commission, he gave Noah an ark. In this, God was perfectly just. Missions, of any sort, is a grace of God. The world is no more entitled to it than a serial rapist is entitled to a Presidential pardon.
We may summarize these things with a simple comparison between Genesis 12 and Matthew 28. To Abraham, the Great Commission was a promise, an impossibility, and a grace. To us, the Great Commission is a reality and a command, but it is still a grace.