A.T. Robertson Commentary John 8:21

"He said therefore again unto them, I go away, and ye shall seek me, and shall die in your sin: whither I go, ye cannot come." — John 8:21 (ASV)

Again (παλιν). Probably παλιν (again) in verse 12 refers to a day after the feast is over since the last day is mentioned in 7:37. So then here again we probably move on to another day still beyond that in verse 12.

And ye shall seek me (κα ζητησετε με). As in 7:34, "the search of despair" (Bernard), seeking for the Messiah when it is too late, the tragedy of Judaism today (1:11).

And ye shall die in your sin (κα εν τη αμαρτια υμων αποθανεισθε). Future middle indicative of αποθνησκω which is the emphatic word here (cf. Ezekiel 3:18; 18:18; Proverbs 24:9). Note singular αμαρτια (sin) here, but plural αμαρτιαις (sins) when the phrase is repeated in verse 24 (sin in its essence, sin in its acts).

Ye cannot come (υμεις ου δυνασθε ελθειν). Precise language of 7:34 to the Jews and to the apostles in 13:33.