The apostle Paul wrote that the resurrection from the dead is the cornerstone of the Christian faith.
But if there is no resurrection of the dead, not even Christ has been raised; 14 and if Christ has not been raised, then our preaching is vain, your faith also is vain. 15 Moreover we are even found to be false witnesses of God, because we testified against God that He raised Christ, whom He did not raise, if in fact the dead are not raised. 16 For if the dead are not raised, not even Christ has been raised; 17 and if Christ has not been raised, your faith is worthless; you are still in your sins. 18 Then those also who have fallen asleep in Christ have perished. 19 If we have hoped in Christ in this life only, we are of all men most to be pitied. 20 But now Christ has been raised from the dead, the first fruits of those who are asleep. 1 Corinthians 15:13-20 (NASB)
Jesus offered himself as an offering for our sin by dying on the cross. Without the resurrection from the dead, he would be just another tragic and delusional historical figure who thought he was something special, when he was only a man, just like everyone else.
However, Jesus’ glorious resurrection was proof positive that his sacrifice had been accepted by his Father in heaven, who vindicated him in the eyes of his disciples.
His Second Coming at the culmination of time will glorify and vindicate him in the eyes of everyone else.
Jesus foretold his own resurrection on multiple times. He told his disciples that he would be put to death on a cross and rise again.
And he began to teach them that the Son of Man must suffer many things and be rejected by the elders and the chief priests and the scribes and be killed, and after three days rise again. Mark 8:31 (ESV)
He told them that he would be raised from the dead as a sign prefigured in the book of Jonah.
But he answered them, “An evil and adulterous generation seeks for a sign, but no sign will be given to it except the sign of the prophet Jonah. 40 For just as Jonah was three days and three nights in the belly of the great fish, so will the Son of Man be three days and three nights in the heart of the earth. Matthew 12:39-40 (ESV)
He told his enemies that if they destroyed the temple of his body, God would raise him up again.
The Jews then said to Him, "What sign do You show us as your authority for doing these things?" 19 Jesus answered them, "Destroy this temple, and in three days I will raise it up." 20 The Jews then said, "It took forty-six years to build this temple, and will You raise it up in three days?" 21 But He was speaking of the temple of His body. 22 So when He was raised from the dead, His disciples remembered that He said this; and they believed the Scripture and the word which Jesus had spoken. John 2:18-22 (NASB)
Jesus told Martha that he would raise Lazarus from the dead because he was and is the embodiment of the resurrection.
Martha then said to Jesus, "Lord, if You had been here, my brother would not have died. 22 "Even now I know that whatever You ask of God, God will give You." 23 Jesus *said to her, "Your brother will rise again." 24 Martha *said to Him, "I know that he will rise again in the resurrection on the last day." 25 Jesus said to her, "I am the resurrection and the life; he who believes in Me will live even if he dies, 26 and everyone who lives and believes in Me will never die. Do you believe this?" John 11:21-26 (NASB)
He promised his disciples that one day he would raise each of us from the dead.
And this is the will of him who sent me, that I should lose nothing of all that he has given me, but raise it up on the last day. 40 For this is the will of my Father, that everyone who looks on the Son and believes in him should have eternal life, and I will raise him up on the last day.” John 6:39-40 (ESV)
Not only did Jesus rise from the tomb after dying for our sins, he is the Resurrection. Those who put their faith and allegiance in him will participate in his resurrection both now, in a spiritual sense, and physically at the Second Coming. Jesus is the resurrection and the life!