What is the Gospel?

Mark 1:14-17   (New International Version)
¹⁴ After John was put in prison, Jesus went into Galilee, proclaiming the good news of God. ¹⁵ “The time has come,” he said. “The kingdom of God has come near. Repent and believe the good news!” ¹⁶ As Jesus walked beside the Sea of Galilee, he saw Simon and his brother Andrew casting a net into the lake, for they were fishermen. ¹⁷ “Come, follow me,” Jesus said, “and I will send you out to fish for people.”

Mark 8:27-38
²⁷ Jesus and his disciples went on to the villages around Caesarea Philippi. On the way he asked them, “Who do people say I am?”
²⁸ They replied, “Some say John the Baptist; others say Elijah; and still others, one of the prophets.”
²⁹ “But what about you?” he asked. “Who do you say I am?”
Peter answered, “You are the Messiah.”
³⁰ Jesus warned them not to tell anyone about him.
³¹ He then began to teach them that the Son of Man must suffer many things and be rejected by the elders, the chief priests and the teachers of the law, and that he must be killed and after three days rise again. ³² He spoke plainly about this, and Peter took him aside and began to rebuke him.
³³ But when Jesus turned and looked at his disciples, he rebuked Peter. “Get behind me, Satan!” he said. “You do not have in mind the concerns of God, but merely human concerns.”
³⁴ Then he called the crowd to him along with his disciples and said: “Whoever wants to be my disciple must deny themselves and take up their cross and follow me. ³⁵ For whoever wants to save their life will lose it, but whoever loses their life for me and for the gospel will save it. ³⁶ What good is it for someone to gain the whole world, yet forfeit their soul? ³⁷ Or what can anyone give in exchange for their soul? ³⁸ If anyone is ashamed of me and my words in this adulterous and sinful generation, the Son of Man will be ashamed of them when he comes in his Father’s glory with the holy angels.”

Additional Scriptures used in this sermon (NIV unless otherwise noted):

Matthew 7:21-23
²¹ “Not everyone who says to me, ‘Lord, Lord,’ will enter the kingdom of heaven, but only the one who does the will of my Father who is in heaven. ²² Many will say to me on that day, ‘Lord, Lord, did we not prophesy in your name and in your name drive out demons and in your name perform many miracles?’ ²³ Then I will tell them plainly, ‘I never knew you. Away from me, you evildoers!’

John 6:46
⁴⁶ “Why do you call me, ‘Lord, Lord,’ and do not do what I say?