In his book “Kingdom of God”, John Bright writes the following:
Although the New Testament teaches us that the people of Christ’s Kingdom are his obedient followers, his Church, there is never the slightest hint that the visibly existing church can either be or produce that Kingdom.
There is no tendency in the New Testament to identify the visible church with the Kingdom of God.
The church that makes such an identification will soon begin to invite God to endorse its own very human policies and practices, will equate the people of God with those nice people who share its particular beliefs and participate in its services, and will reckon the advance of the Kingdom in terms of its numerical growth. But it will not be the New Testament church!
Such an identification is a great snare, as prophets since Amos have told us. It only fathers the fatuous conceit of rightness with God by external conformity, and the equally fatuous expectation of divine protection -- for, forsooth, this is his church! Not so the New Testament!
The Church is indeed the people of the Kingdom of Christ, but the visible church is not that Kingdom. On the contrary, let it take heed to itself, lest by its behavior it becomes so much lukewarm water to be spewed out of the mouth of God (Rev. 3:16)! Let it live in full awareness that it, too, is under the judgment of God (Rom. 2:5; 14:10; I Cor. 3:13; 4:5; 11 Cor. 5:10). It, too, the new and pure Israel, must be purged!
The church is like a wheatfield in which a good many weeds have come up (Matt. 13:24-30). Weeds and wheat now grow side by side in it, but God (and only God: vss. 28-29!) will know how to separate them. (The Kingdom of God, John Bright, page 236)