Tradition tells us that 11 of the 12 disciples died as martyrs for preaching the message of Jesus. Why would anyone die for a lie? At first the disciples didn’t believe in Jesus. When Jesus was arrested, they all forsook him and fled (Mark 14:50). It was only when Jesus rose from the dead that they really believed everything Jesus said was true (John 2:1922). After that they were no longer timid; they gave witness to the resurrection of Jesus with great power (Acts 4:33) and were even ready to die for what they believed in. Therefore, it is very unlikely that the disciples would lie as they sealed their witness with their blood!
Even the Quran attest to the disciples of Jesus as honest helpers of God (Surah 61:14, 3:52)