As the kingdom of heaven was approaching, John called on these people to repent. It was common knowledge to John's Jewish listeners that the promised Messiah would one day establish a new kingdom. Jesus will be referred to by John as the Messiah, along with the imminent establishment of His kingdom. During his sermon, John emphasized that in order to be included in this kingdom, his Jewish listeners must turn from sin. 
As a result of the shock of Israel's rejection of their Messiah-King and their refusal to repent, the kingdom was not established at the appointed time by God. In spite of this, it secured salvation for the Gentile nations. Throughout the past 2000 years, men and women have been saved by grace through faith in the gospel of Jesus Christ. As the Body of Christ, the Church has been used by God to further His glorious plan of redemption and to make disciples of all nations. 
In the near future, the dispensation of grace will come to an end, and Christ will remove His Church from the scene of world events. Eventually, Israel will be able to fulfill its God-given mission of preaching the gospel of the kingdom throughout the entire world.

Dear Heavenly Father, You have blessed us with the Gospel of Matthew that gives us an insight into the life and times of Jesus during His first advent. Thank You for entrusting the Church with the message of salvation for a lost and dying world. Thank You for the future day when Christ will return to earth and establish the kingdom of heaven here. Repentance and recognition of Jesus as Messiah and King will occur all around the world. 
In Jesus's name I pray. Amen.