“And where I am going, you know the way there.”
He first stresses that they know the way to where He is going, an that where He is going is to His Father's dwelling place. He has previously taught them, and revealed to them, the way into the Father's favour and presence through ‘eating and drinking' Him by response to His words (John 4:13-14; John 6:35; John 7:38). Now He stresses in an even deeper sense that He is ‘the way'. It is by personal response to Him as the Way that they will know truth and life. So when He has gone they need not fear, for the way will still be the same. He has shown them the way there, the way to eternal life, through believing fully in Him (John 3:15-16; John 7:38), and that is the way that they must take.
(The above rendering is probably the correct one, but many very good authorities have ‘you know where I am going and you know the way there', which ties in more specifically with the words of Thomas. It is this very fact however which makes it the easier reading, thus making it more suspect as such an alteration is more likely. In view of the manuscript evidence the change must have occurred very early on. Papyrus 66, a very early testimony to the text, has our reading in the text and the alteration in the margin).