John Gills Exposition of the Bible Commentary

Verse 21 (John 8:21)

Then said Jesus again unto them ,.... It may be, immediately after he had said the above words; or rather some time after, it may be on the same day:

I go my way ; meaning, the way of all flesh, or that he should die: the way of speaking shows, that his death was certain, a determined thing; which must be, and yet was voluntary: he was not driven, nor forced, but went freely; this being the path, the way, through which he must enter into his kingdom and glory:

and ye shall seek me ; that is, shall seek the Messiah, as their deliverer and Saviour, when in distress; and whom he calls himself, because he was the true Messiah, and the only Saviour and Redeemer of his people, in a spiritual sense; otherwise they would not, nor did they seek Jesus of Nazareth:

and shall die in your sins ; or "in your sin"; so it is in the Greek text, and in the Vulgate Latin, and Persic versions: meaning, in their sin of unbelief, and rejection of him the true Messiah: the sense is, that in the midst of their calamities, which should come upon them, for their sin against him, they should in vain seek for the Messiah, as a temporal deliverer of them; for their nation, city, and temple, and they therein should utterly perish, for their iniquity; and their ruin would not only be temporal, but eternal: since it follows,

whither I, go ye cannot come , signifying, that whereas he was going to his Father, to heaven and glory; to enjoy eternal happiness at his Father's right hand, in the human nature; they should never come there, but whilst many sat down in the kingdom of heaven, with their fathers Abraham, Isaac, and Jacob, who should come from afar, they would be shut out, and not suffered to enter in.

- John Gills Exposition of the Bible Commentary