In 1 Corinthians 15: 3,4
Christ died for our sins according to the scriptures, and that he was buried, and that he was raised on the third day according to the scriptures,
Jesus' words in Mark 1:15 come in the form of an urgent command: "The time is fulfilled, and the Kingdom of God is at hand. Repent, and believe in the gospel." After His resurrection from the dead, He tells His disciples: Thus it is written, and thus it was necessary for the Christ to suffer and to rise from the dead the third day, and that repentance and remission of sins should be preached in His name to all nations, beginning at Jerusalem. (Luke 24:46-47)
Notice that following repentance is the remission of sins (Romans 6:1-12). This is why on Pentecost, AD 31, Peter instructs the assembled crowd, "Repent, and let every one of you be baptized in the name of Jesus Christ for the remission of sins; and you shall receive the gift of the Holy Spirit" (Acts 2:38).
