'Besides revealing a seriously deficient view of Scripture, this contrast between Jesus and Paul rests on a misunderstanding of our Lord's teaching concerning the kingdom. Jesus's proclamation of the kingdom is identitical to Paul's proclamation of the gospel of justification. Contrasting the kingdom with the church is another way of saying that the main point of Jesus's commission consists in our social action rather than the public ministry of the Word and sacrament. In other words, it's another way of saying that we are building the kingdom rather than receiving it; that the kingdom of God's redeeming garce is actually a kingdom of our redeeming works.'
Michael Horton, The Gospel Commission, p.75.