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. “The Lord reigns; let the earth rejoice; let the many coastlands be glad!” (Ps 97:1). “Let the peoples praise thee, O God; let all the peoples praise thee! Let the nations be glad and sing for joy!” (Ps 67:3-4).
But worship is also the fuel of missions. Passion for God in worship precedes the offer of God in preaching. You can’t commend what you don’t cherish. Missionaries will never call out, “Let the nations be glad!” who cannot say from the heart, “I rejoice in the Lord…I will be glad and exult in thee, I will sing praise to thy name, O Most High” (Ps 104:34, 9:2). Missions begins and ends in worship.”
–John Piper, Let the Nations Be Glad! The Supremacy of God in Missions (Grand Rapids: Baker, 1993/2003), 17.