Moreover, brethren, I declare unto you the gospel which I preached unto you, which also ye have received, and wherein ye stand;
2 By which also ye are saved, if ye keep in memory what I preached unto you, unless ye have believed in vain.
3 For I delivered unto you first of all that which I also received, how that Christ died for our sins according to the scriptures;
4 And that he was buried, and that he rose again the third day according to the scriptures: 1 Corinthians 15:1-4
WHY IS THIS THE GOSPEL?
1 Corinthians 1:23 But we preach Christ crucified, unto the Jews a stumblingblock, and unto the Greeks foolishness;
Because we preach Christ crucified.
1 Corinthians 2:2 For I determined not to know any thing among you, save Jesus Christ, and him crucified.
1 Timothy 1:15 This is a faithful saying, and worthy of all acceptation, that Christ Jesus came into the world to save sinners; of whom I am chief.
Romans 6:23 For the wages of sin is death; but the gift of God is eternal life through Jesus Christ our Lord.
Colossians 1:5 For the hope which is laid up for you in heaven, whereof ye heard before in the word of the truth of the gospel; 6Which is come unto you, as it is in all the world; and bringeth forth fruit, as it doth also in you, since the day ye heard of it, and knew the grace of God in truth: