Hebrews 6:1 Therefore let us leave the elementary teachings about Christ and go on to maturity, not laying again the foundation of repentance from acts that lead to death, and of faith in God, 2 instruction about baptisms, the laying on of hands, the resurrection of the dead, and eternal judgment.
Why is Christianity the one true faith? Jesus Christ's resurrection from the dead on the third day just as He told us is the reason Christianity is the one true faith. There are many religions in the world claiming to be true. The current one in the news all the time is Islam. The Muslims (people who practice Islam are called Muslim) persecute Christians and deny that any man can die for the sins of another person. Muslims claim to be the only true religion. Jesus' resurrection from the dead on the third day settles the dispute between Islam and Christianity. Jesus' resurrection from the dead proves Christianity is the one true faith, that Jesus is the one true God (see note), and that the Bible is the one true book concerning eternal and abundant life.
In Luke 9:22 Jesus said, "The Son of Man must suffer many things and be rejected by the elders, chief priests and teachers of the law, and must be killed and on the third day be raised to life." Luke 24:6-7 records the fact that Jesus did rise from the dead on the third day, "He is not here! He has risen! Remember how He told you, while He was still with you in Galilee: 'The Son of Man must be delivered into the hands of sinful men, be crucified and on the third day be raised again.'"
John 2:18-22 validated Christianity as the one true faith and the Bible as God's word to sinful people. "Then the Jews demanded of Him, 'What miraculous sign can you show us to prove your authority to do all this?' Jesus answered them, 'Destroy this temple and I will raise it in three days.' The Jews replied, 'It has taken forty-six years to build this temple and you will raise it in three days?' But the temple He had spoken of was His body. After He was raised from the dead, His disciples recalled what He had said. Then they believed the Scriptures and words that Jesus had spoken."
Note: Jesus is called the Son of Man and the Son of God. Matthew 1:23 instructs us that Jesus is God. The creator God has revealed Himself to us as Father, Son and Holy Spirit. Matthew 28:19 instructs us to baptize in the name (singular) of the Father, Son, and Holy Spirit. God is one God revealed as Father, Son, and Holy Spirit.