John 12:50

‘And what I say, therefore, I say as the Father has told me I must'.

Jesus confirms that all He has said has been because God has instructed Him in what to say and has made Him say it under the divine necessity. He is God's mouthpiece, God's voice.

So John stresses at the end of this section which began with John 1:1, and ends here, both the Messiahship and Sonship of Jesus, and the essence of His teaching, along with the certainty that it has come directly from the Father, and is in accordance with His Father's instruction. This is the message for which He will die, and now His ministry is complete He can go on to the preparation of His disciples for His final act.