I Corinthians 15:3-7, 14-17
 
I passed on to you what was most important and what had also been passed on to me. Christ died for our sins, just as the Scriptures said.  He was buried, and he was raised from the dead on the third day, just as the Scriptures said.  He was seen by Peter and then by the Twelve.  After that, he was seen by more than 500 of his followers at one time, most of whom are still alive, though some have died. Then he was seen by James and later by all the apostles.
 
And if Christ has not been raised, then all our preaching is useless, and your faith is useless.  And we apostles would all be lying about God—for we have said that God raised Christ from the grave.  And if Christ has not been raised, then your faith is useless and you are still guilty of your sins.  In that case, all who have died believing in Christ are lost!  And if our hope in Christ is only for this life, we are more to be pitied than anyone in the world.