44 Then Jesus cried out, "When a man believes in me, he does not believe in me only, but in the one who sent me.
45 When he looks at me, he sees the one who sent me.
46 I have come into the world as a light, so that no one who believes in me should stay in darkness.
Why is this a favourite passage?
I see this as the basic claim of Christianity - in Jesus we see God.
As will become clear as this series goes on, John is my favourite gospel (even though I accept it is less historically 'straight' than the others). This passage comes at what is effectively the mid-point of the book, the turning point of the gospel as a whole. Up until this time John has been describing Jesus' public ministry - the signs of power that Christ accomplished to give a witness to his nature, so, the turning of water into wine, overturning the tables in the temple, the feeding of five thousand, the raising of Lazarus and so on. From this point Jesus' public ministry is complete, and the remainder of the gospel has two elements - Jesus teaching the disciples in what is called the 'farewell discourse', and then the story of Holy Week. So this text is a hinge - it looks back to Christ's public ministry, and forward to his teaching of the disciples.
I would pick out three elements from the text. The first is that there is continuity between the Father and the Son - Christ is the way to the Father. If this wasn't true then Christianity would be idolatrous - the raising up of a creature to the rank of creator.
The second is verse 45 which underlies the theology of icons, as used in the Eastern Orthodox churches. Think of looking through Christ, as you look through a window - for Christ is wholly transparent to God, when you look at him, you look at the one who sent him.
Finally we have the 'mission statement' from Christ - I have come into the world as light, that no-one who believes in me should stay in darkness. Christ illuminates our lives; he shows us the nature of God and of humanity - and so our own nature becomes clearer as a result. Our way becomes clearer, a way which Christ shows to us in his own life. The question is whether we turn towards the light or away from the light. The Christian calling as disciples is to trust in the light so that we might become children of light - and then we will be transparent to God too; living icons of the Father.