Matthew 20:17 And as Jesus was going up to Jerusalem, he took the twelve disciples aside, and on the way he said to them, 18 "See, we are going up to Jerusalem. And the Son of Man will be delivered over to the chief priests and scribes, and they will condemn him to death 19 and deliver him over to the Gentiles to be mocked and flogged and crucified, and he will be raised on the third day."
Jesus kept telling His disciples what was going to happen to Him in order for Him to complete His assignment from God. Why did He keep telling them? John records the answer in John 2:22 "When therefore He was raised from the dead, His disciples remembered that He had said this, and they believed the scriptures and the word that Jesus had spoken."
We believe the scriptures and the word Jesus has spoken, which is now recorded in the Bible, because what Jesus said happened. Jesus said He would be crucified and raised from the dead on the third day and it happened (Luke 24:6-9). The death of Christ for our sins on the cross was proved sufficient by His resurrection from the dead, proving He had defeated sin and death (Romans 4:23-25). He rendered sin and Satan powerless on the cross (Romans 6:6-7; Hebrews 2:14-15) and proved it by rising from the dead. Jesus also said all who believed in Him would receive the Holy Spirit when He ascended (John 16:7). This happened to the first believers and happens to each of us who believe today. Every one who believes the gospel receives the Holy Spirit and has the power to live a new life (Ephesians 1:13-14, 19-20; 3:20).
The resurrection of Jesus on the third is the basis for our belief in the truth of the Bible. Let's take God at His word, obey by faith in the Son of God and live a new life for all to see and believe the gospel.