[Jesus continued,] "But I will send you the Advocate — the Spirit of truth. He will come to you from the Father and will testify all about me. And you must also testify about me because you have been with me from the beginning of my ministry."
— John 15:26-27 NLT
The apostles of Jesus are trustworthy witnesses to the life, teaching, and will of Jesus for several reasons. Jesus mentions two crucial reasons here. Later, after Jesus' resurrection, the apostles give the third one:
- Jesus sent them the Holy Spirit to ensure their trustworthiness with the truth and bless them with heavenly insight.
- They had been with Jesus from the beginning, knowing his word and observing his life.
- Not only that, the apostles and others were eye witnesses of Jesus' being alive after his resurrection from the dead. 
By selecting apostles and then sending them the Spirit to continue his work and teaching through them, Jesus made sure that others would be left to start his church and teach his truth. So let's listen to them as they reveal Jesus to us!
Holy and righteous Father, thank you for leaving reliable and inspired witnesses to Jesus' life. I thank you for their stories of Jesus and their desire to bless future generations of your people. Make me more passionate to know your will that is revealed through their accounts of the life and teaching of Jesus, in whose name I pray. Amen.