A.T. Robertson Commentary John 20:19

"When therefore it was evening, on that day, the first [day] of the week, and when the doors were shut where the disciples were, for fear of the Jews, Jesus came and stood in the midst, and saith unto them, Peace [be] unto you." — John 20:19 (ASV)

When therefore it was evening on that day (ουσης ουν οψιας τη ημερα εκεινε). Genitive absolute with οψια (οψιος, late), old word with ωρα (hour) understood and here for the time from six to nine (6:16) and the locative case of time with ημερα (day). John often uses this note of time (1:39; 5:9; 11:53; 14:20; 16:23,26). The addition of τη μια σαββατων (see 20:1 for this use of μια like πρωτη) proves that John is using Roman time, not Jewish, for here evening follows day instead of preceding it.

When the doors were shut (των θυρων κεκλεισμενων). Genitive absolute again with perfect passive participle of κλειω, shut to keep the Jews out. News of the empty tomb had already spread (Matthew 28:11). See Joh 7:13 for the phrase "for fear of the Jews"; cf. 12:42.

Stood in the midst (εστη εις το μεσον). Second aorist (ingressive) active (intransitive) of ιστημ, "stepped into the midst."

Peace be unto you (Ειρηνη υμιν). The usual oriental salutation as in verses 21,26; Luke 24:36, here with probable reference to Joh 14:27 (Christ's legacy of peace).