When Jesus speaks we listen. That makes sense, right? Jesus is the one to whom all authority in heaven and earth has been given (Matthew 28:18). Jesus is the one of whom it will be said, forever, "Worthy is the Lamb who was slain, to receive power and wealth and wisdom and might and honor and glory and blessing!" (Revelation 5:12). He's the one to whom every knee will bow (Philippians 2:10) — the one by whom all the tribes of the earth will wail (Revelation 1:7), and from whom the fury of God's wrath will be executed (Revelation 19:15).
Jesus has that kind of supremacy — so what he says matters.
And beyond that, we've been united to Jesus by faith (Romans 6:5), made alive in him by grace (Ephesians 2:4–5), counted righteous in him because of his work (Galatians 2:16). Jesus, in all of his supremacy, is also our shepherd — so we know his voice (John 10:27).
Therefore, by virtue of his power and grace, because he is the Sovereign and our Savior, when he tells his church to make disciples of all nations, we really want to do that.
Toward a Definition
Jesus commissions us to "go" — because of his authority — "and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, teaching them to observe all that I have commanded you" (Matthew 28:19–20).
[Read the rest of the article at Desiring God.]