The word repent literally means "to change the mind," "to have second thoughts" or "to regret."  The basic meaning of "a change of mind" still exist in New Testament usage, but in a context of accepting Christ by faith.  For example:  "Testfying both to the Jews and also to the Greeks, repentance [metanoia] toward God, and faith toward our Lord Jesus Christ" (Acts 20:21).  Repentance is so clearly related to believing that many review it as a reverse side of "the coin of faith."  That is, one cannot truly believe in Christ as savior without changing one's mind about one's rellationship to Him.

   The Christian era started when John the Baptist, the Messiah's forerunner, called on Israel, saying, "Repent, for the kingdom of heaven is at hand." (Matthew 3:2).  He added, "Bring forth therefore fruits meet for repentance" (Matthew 3:8).  The change  should be visible to others.  After being tempted by Satan in the wilderness, our Lord repeats the same message:  "Repent: for the kingdom of heaven  is at hand" (Matthew 4:17).

   At Pentecost Peter opened the Christian era with a call to Israel to repent of crucifying the Messiah and to express that change by being baptized with water (Acts 2:38)  Then Peter said unto them.  Repent and be baptized every one of you in the name of Jesus Christ for the remission of sins, and you shall receive the gift of the Holy Ghost.  God is good to us in order to lead us to repentance (Romans 2:4) Or despised you the riches of His goodness and forebearance and longsuffering not knowing that the goodness of God leads you to repentance.   God's desire is "that all should come to repentance"  (2 Peter 3:9).

   Repentance is prominent in Revelation, especially in the letters to the churches.  People in churches often desperately need to repent. Hardened latter-day sinners undergoing God's wrath against a Christ-rejecting world are four times said not to repent (Revelation 9:20, 21;  16:9,11)  "And the rest of the  men who were not killed by these plagues yet repented not of the works of their hands, that they should not worship  devils, and idols of gold, and silver, and brass, and stone, and of wood: which neither can see, nor hear, nor walk.  Neither repented they of their murders, not of their sorceries, nor of their fornication, nor of their thefts."

"And men were scorched with great heat, and blasphemed the name of God, which has power over these plagues: and they repented not to give Him glory.  And blasphemed the God of heaven because of their pains and their sores, and repented not of their deeds."