1 Corinthians 15:16-19

16 For if the dead are not raised, not even Christ has been raised. 17And if Christ has not been raised, your faith is futile and you are still in your sins.  18 Then those also who have fallen asleep in Christ have perished. 19If in Christ we have hope in this life only, we are of all people most to be pitied.

Acts 1:3

3 He presented himself alive to them after his suffering by many proofs, appearing to them during forty days and speaking about the kingdom of God.