When Paul was writing to the Corinthians he laid everything on the line regarding the resurrection,

"For if the dead are not raised, not even Christ has been raised; and if Christ has not been raised, your faith is worthless; you are still in your sins." (1 Corinthians 15:16-17)

In this passage Paul makes a rhetorical statement using the fact of Christ's resurrection to support the concept of resurrection. In order to use this argument there could have been no question that Christ had been raised. If there was any disbelief, not only would his argument have been in vain, but he may have caused doubts among them about Christ. Numerous other passages grant the same assumption,

"For if we have become united with Him in the likeness of His death, certainly we shall also be in the likeness of His resurrection," (Romans 6:5)

"But if the Spirit of Him who raised Jesus from the dead dwells in you, He who raised Christ Jesus from the dead will also give life to your mortal bodies through His Spirit who dwells in you." (Romans 8:11)

"For they themselves report about us what kind of a reception we had with you, and how you turned to God from idols to serve a living and true God, and to wait for His Son from heaven, whom He raised from the dead, that is Jesus, who rescues us from the wrath to come." (1 Thessalonians 1:9-10)