Chapter 13 of Matthew's Gospel is full of parables of Jesus teaching about the Kingdom of God, usually beginning with the words, "The Kingdom of God is like." The parable of the wheat and the weeds at vv. 24-30 talks about how in the church and in this life the wicked and the righteous are growing up together until the final judgment of God. Tares, or darnel, looks like wheat, but it is poisonous.
The great Anglican Bishop J.C. Ryle, in his "Expository Thoughts on the Gospels," described the Kingdom of God as the spiritual reign of Christ over the hearts of believers. This kingdom, though currently small and often despised, will ultimately be great and glorious at Christ's second coming.
Ryle explained the Kingdom of God is not just a future hope but a present reality. All true believers are subjects of this kingdom, living under Christ's rule and striving to reflect His teachings in their lives.