3 But on hearing these words, as is usual with those whose thoughts are carnal, who judge after the flesh, and hear and apprehend everything in a carnal way, they said, “Will he kill himself because he said, Whither I go ye cannot come.” Foolish words, and overflowing with stupidity! For why could they not go whither He would have proceeded had He killed Himself? Were not they themselves to die? What, then, means, “Will he kill himself because he said, Whither I go ye cannot come?” If He spoke of man's death, what man is there that does not die? Therefore, by “whither I go” He meant, not the going to death, but whither He was going Himself after death. Such, then, was their answer, because they did not understand.
Source: Tractates on the Gospel of John (New Advent)