Repentance and the Gospel

It is interesting to observe that both times when the gospel is first mentioned in Mark's gospel, it is preceded with repentance.

First are John the Baptist's words:

John the Baptist appeared in the wilderness preaching a baptism of repentance for the forgiveness of sins.
 --Mark 1:4

Then the first preaching of Jesus:

14 Now after John had been taken into custody, Jesus came into Galilee, preaching the gospel 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

21 He made the One who did not know sin to be sin for us, so that we might become the righteousness of God in Him.
--2 Cor 5:21


18 For the message of the cross is foolishness to those who are perishing, but to us who are being saved it is the power of God.
--1 Cor 1:18

18 If the world hates you, you know that it hated Me before it hated you. 
19 If you were of the world, the world would love its own.
--John 15:18

34 Think not that I am come to send peace on earth: I came not to send peace, but a sword.
--Mat 10:34

4 ...Do you not know that friendship with the world is enmity with God? Whoever therefore wants to be a friend of the world makes himself an enemy of God.
--James 4:4