Missions is not the ultimate goal of the church. Worship is. Mission exists because worship doesn’t. Worship is ultimate, not missions, because God is ultimate, not man. When this age is over, and the countless millions of the redeemed fall on their faces before the throne of God, missions will be no more. It is a temporary necessity. But worship abides forever. Worship, therefore, is the fuel and goal of missions. It’s the goal of missions because in missions we simply aim to bring the nations into the white hot enjoyment of God’s glory. The goal of missions is the gladness of the peoples in the greatness of God. (Let the Nations Be Glad, 2004, p.17).I sympathise with piper on this point. Worship and the Glory of God definitely have something to do with mission. In Romans 1 God justly judges humans everywhere who neither thanked him or worshiped him. And a great eschatological vision in the scriptures is of "the whole earth being filled with the glory of God as the waters cover the sea" (Isaiah 11.9 and Habbakuk 2.14).
But something in Piper's statement irks me. Maybe it's a reaction against Piper's reduction of everything to glory - I'm not sure what it is, but the biblical theologian in me whats to nuance Piper's thesis. Maybe something like: Mission exists because evil does. On reflection this does sound pretty similar to Piper, but I'm trying to locate mission within the framework of the biblical narrative. (I'm not convinced that Piper does this in Let the Nations be Glad, largely because the first reference to Genesis 12 is on page 30 and is talking about the Puritans. When he does get back to Gen 12 around page 130, this foundational text only rates a passing mention). Mission is God's plan to redeem humanity and creation from the captivity of evil and sin: idolatry, hatred, famine, death, etc. In the proto-gospel, the promise is the crushing of evil: "I will put enmity between you and the woman, and between your offspring and her offspring; he shall bruise your head, and you shall bruise his heel” (Genesis 3.15). God works through Abraham and Israel and finally Jesus to make this happen. In Abraham all the nations will be blessed. Israel is a light to the nations (never mind for now that she constantly failed this) and the "nations will stream to her". And Jesus is able to totally obliterate evil cf. Colossians 2.15. My point is that mission is not just a New Testament concept, it's deeply ingrained in the story of the bible.
But then again, I'm not sure I'm entirely happy with: "Mission exists because evil does". Forgetting issues of theodicy for now, there is a sense in which mission exists because God does. God creates the world ex nihlo, making something out of nothing. He separates light from darkness, gives shape to a world that is formless and void. And just before God rests, he creates Man and Woman in his image and charges them with a mission: "Be fruitful and multiply and fill the earth and subdue it and have dominion over the fish of the sea and over the birds of the heavens and over every living thing that moves on the earth" (Genesis 1.28). I take it that this mission of reflecting the image of God into the world continues despite the 'the fall'. It's given fresh impetuous by Jesus who commanded his disciples to go and make disciples of all nations - so that everyone will hear that Jesus is King and we should reflect his image. And I take it that this will continue in some form in the new creation, after Jesus reigns unchallenged and sin and death are no more. And this to me seems to be a more complete "justification" for mission.