God sent John the Baptist to prepare the Jews for Jesus.   He preached a simple message:  In those days John the Baptist came preaching in the wilderness of Judea, and saying, ‘Repent, for the kingdom of heaven is at hand!’  For this is he who was spoken of by the prophet Isaiah, saying: ‘The voice of one crying in the wilderness: 'Prepare the way of the Lord; Make His paths straight.'” (Matt 3:1-3).

Herod Antipas put John in prison, after which Jesus began His ministry with the same invitation.  Mark’s gospel begins, “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).

In both cases, the Greek word translated repent” literally means “to think different, to reconsider.”  John the Baptist and Jesus were telling people that they had to think differently to be part of the kingdom of God.

People naturally think about physical things, like what to eat or wear.   They think about their home, their livelihood, and how to improve both.  The Bible puts it this way,

Those who live according to the flesh set their minds on the things of the flesh” (Rom 8:5).

Concentrating thoughts on needs and circumstances tend to make people selfish.   This tendency causes arguments, anger, and fights.  It can lead to immorality.  Apostle Paul confessed, We all once conducted ourselves in the lusts of our flesh, fulfilling the desires of the flesh and of the mind, and were by nature children of wrath, just as the others” (Eph 2:3). 

People’s natural thought processes bring difficulties.  The Bible explains: “There is a way that seems right to a man, but its end is the way of death” (Prov 14:12).  Elsewhere, it says, “To be carnally minded is death” (Rom 8:6).  When people are left to their own thought processes, they always bring difficulties and disasters on themselves.

Jesus taught that people must change how they think.  Otherwise, they could not receive the kingdom of God.  Paul explained The natural man does not receive the things of the Spirit of God, for they are foolishness to him; nor can he know them, because they are spiritually discerned” (1 Cor 2:14).

God’s ways are different from human ways.  The Bible reveals, “‘My thoughts are not your thoughts, Nor are your ways My ways,’ says the Lord.  ‘For as the heavens are higher than the earth, So are My ways higher than your ways, And My thoughts than your thoughts’” (Is 55:8-9).  If people want to live in the kingdom of God, they must change how they think.  They must repent.  

When someone believes Jesus enough to trust Him they become willing to change how they think.  They are willing to reconsider how they live.  They repent.  But by changing our thought processes to match Jesus’ thought process, we prepare ourselves to live in His kingdom.