Summary
And if Christ has not been raised, your faith is futile; you are still in your sins. - 1 Corinthians 15:17
He was delivered over to death for our trespasses and was raised to life for our justification. - Romans 4:25
If Christ was not raised, then there is no basis for our faith and it is useless. Without the resurrection we are still in our sins and are not justified.
Biblical Support
Explanation
The resurrection is the confirmation that Jesus’ sacrifice accomplished its purpose. Without it, faith would be empty, and sin would still enslave us. His resurrection secures our justification and confirms the completion of His saving work.
The resurrection is necessary for our salvation.