John Gill Commentary John 14:4

"And whither I go, ye know the way." — John 14:4 (ASV)

And where I go you know
They might have known, at least, where he was going, since he had spoke of his Father's house, and of his going to prepare a place for them there, and doubtless had some knowledge of it, though very confused and imperfect:

and the way you know :
this also they might have known from some expressions of his, that the way to his Father's house lay through sufferings and death, in which way they also were to follow him to his kingdom and glory. Though these words may be understood as an interrogation, "and where I go do you know? and the way do you know?" which best agrees with Thomas's answer, and removes all appearance of contradiction between Christ's words and his.