Paul says it best:
Moreover brethren, I declare unto you the godpel which I preached unto you, which also ye have received, and wherein ye stand;
By which also ye are saved, if ye keep in memory what I preafhed unto you, unless ye have believed in vain.
For I delivered unto you first of all that which I also received, how that Christ died for our sins according to the scriptures;
And that he was buried, and that he rose again the third day according to the scriptures;
And that he was seen of Cephas, then of the twelve:
After that, he was see of above five hundred brethren at once; of whom the greater part remain unto this present [ca. some time in the latte 50's or early 60's A.D.--Uncle Cephas], but some are fallen asleep.
After that, he was seen of James; then of all the apostles.
And last of all he was seen of me also, as of one born out of due time.
(I Corinthians 15:1-8)
Now if Christ be preached that he rose from the dead, how say some among you that there is no resurrection of the dead?
But if there be no resurrection of the dead, then Christ is not risen:
And if Christ be not risen, then is our preaching vain, and your faith is also vain.
Yea, and we are found false witnesses of God; because we have testified of God that he raised up Christ: whom he raised not up, if so be it that the dead rise not...
If in thie life only we have hope in Christ, we are of all men most miserable.
(I Corinthians 15:12-19)
Uncle Cephas urges his readers to go to the Scriptures and read the whole of the Pauline letters. They're worth it.
The resurrection of Jesus Christ is therefore fundamental to the Christian faith. Without it, Paul says, we might as well go home. Indeed, the naturalism of 19th and 20th century liberal theology caused many to join that group which Paul rebuked in Corinth so long ago. The result was the weakening of the churches, the near-suicide of Protestantism, and its replacement by a host of violent "isms" which spilled more blood in the 20th century alone over the right interpretation of Marx than was spilled over wrong theology in the 15 centuries between the conversion of Constantine and the shutting down of the Spanish Inquisition in 1804.
The resurrection of Christ also signals a new beginning for our human race, that there is indeed salvation. So sure were the first apostles of their message that most of them died martyrs proclaiming it. It also tells us that Jesus Christ is indeed the holder of all authority in heaven and on earth, for even death and Hell are subject to him who conquered them--and now witnesses that he is able to save those who trust him from those final horrors.
The resurrection of Jesus Christ also explains the use of Sunday as the day of rest and worship for Christians. Just as the original Sabbath proclaimed the original creation, so the day of resurrection proclaims the new creation (Acts 20:7ff.).
May this, and all other Sundays, be blessed and joyous to you.