1 Corinthians 15:20
But now is Christ risen from the dead, [and] become the firstfruits of them that slept.
Note 1 at 1Co 15:20: The resurrection of Jesus puts Christianity in a class all by itself. Many people have come and gone who have professed some revelation from God or new way of approaching God, but only Jesus has conquered death. This makes Him unique and elevates Him above the level of any other person who has ever walked on the earth. The resurrection of Jesus is the ultimate proof of the accuracy of His doctrine (see note 4 at Ro 1:4).
Note 2 at 1Co 15:20: Paul's use of the word "firstfruits" is very important to his argument for the resurrection. Christ was not the "only fruit" (or person) of the dead, but the "firstfruits." If there is a "firstfruits," then there has to be a second fruit and third fruit, etc. He was saying that Christ was just the first among many to be raised from the dead.
Some may question how Jesus could be the "firstfruits" of the dead, because there were people raised from the dead prior to Jesus (see note 3 at Lu 7:15). However, Jesus was raised from the dead, never to die again. He was the first person ever raised to immortal life. This is what Paul was referring to.