The Hebrew Scriptures spoke frequently of the coming kingdom of God, and when Jesus arrived on the Earth, the time for the kingdom had finally approached,

Now after John was put in prison, Jesus came to Galilee, preaching the gospel of the kingdom of God, and saying, “The time is fulfilled, and the kingdom of God is at hand. Repent, and believe in the gospel” (Mark 1.14–15).

Therefore, the kingdom did arrive in the first century, and now it has spread all over the planet. We more commonly call it, The Church.

Jesus also announced that since the kingdom would be set up during those days, the people were to repent and believe the Gospel, which is the something we must do.