Matthew 4:17 (KJV) From that time Jesus began to preach, and to say, Repent: for the kingdom of heaven is at hand.
“Kingdom of heaven”– this phrase is found only in Matthew. Mark, Luke, and John all use the similar phrase “kingdom of God”. The teaching about God’s kingdom is a very important one in the New Testament. Matthew refers to it nearly 50 times and NT as a whole refers to it about 140 times.
Kingdom of “heaven” indicates a rule that is spiritual and heavenly, having its source in heaven. Kingdom of “God” means God’s rule among men or in men’s hearts. Sometimes God’s kingdom means the outward sphere of His rule, sometimes the inner spiritual rule in the hearts of His believers.
Both John the Baptist and the Lord Jesus spoke of the kingdom as being “near”. This was because Jesus the King from heaven was on the scene and His ministry was beginning. So there would be a new and greater manifestation of God’s rule than was known in Old Testament days.
Know Your Bible 