Do these two terms mean different things? Or are they one and the same?
In Matthew's gospel, something followed the baptism and wilderness experience of Jesus: He officially began His earthly ministry—preaching the gospel of the kingdom and healing the sick (Matthew 4:17–25).
See what He preached:
Matthew 4:17,23(NKJV)
17 - From that time Jesus began to preach and to say, "Repent, for THE KINGDOM OF HEAVEN is at hand."
23 - And Jesus went about all Galilee, teaching in their synagogues, preaching the gospel of the kingdom, and healing all kinds of sickness and all kinds of disease among the people.
See Mark’s account of this same event:
Mark 1:14–15(NKJV)
14 - Now after John was put in prison, Jesus came to Galilee, preaching the gospel of the kingdom of God,
15 - and saying, "The time is fulfilled, and THE KINGDOM OF GOD is at hand. Repent, and believe in the gospel."
We see clearly by comparing these references that the two terms are used interchangeably. Luke records it as “the kingdom of God” (Luke 4:43–44).
Let's see another instance.
In the beatitudes, Jesus spoke forth blessedness on those who are poor in spirit:
Matthew 5:3(NKJV)
"Blessed are the poor in spirit, For theirs is the kingdom of heaven.
See Luke's account of this:
Luke 6:20(NKJV)
Then He lifted up His eyes toward His disciples, and said: "Blessed are you poor, For yours is the kingdom of God.
Let's see one more.
After Jesus counselled a rich young ruler whose eyes were fixated on his riches, the Lord lamented:
Matthew 19:23–24(NKJV)
23 - Then Jesus said to His disciples, "Assuredly, I say to you that it is hard for a rich man to enter the kingdom of heaven.
24 - And again I say to you, it is easier for a camel to go through the eye of a needle than for a rich man to enter the kingdom of God."
We see here how Matthew uses both terms interchangeably in the same narrative.
It is very important to pay good attention to such details as this and avoid getting overexcited by certain “rhema” that propose a difference.
The kingdom of heaven is the kingdom of God.
Matthew 23:22(NKJV)
And he who swears by heaven, swears by the throne of God and by Him who sits on it.
Heaven is God's throne (Isaiah 66:1); God is the King of the kingdom of heaven. This is the kingdom of God.
Victor Ibosiola © 2023