John 20:26

John located this post-resurrection appearance eight days after Easter Sunday, namely, the following Sunday. His "eight days" (Gr. hemeras okto) evidently included both Sundays. Perhaps he identified the day because, by the time John wrote, Sunday had become the day of worship for Christians, when they commemorated Jesus’ resurrection. They worshipped Him on Easter Sunday, then again the following Sunday, and then on succeeding Sundays from then on (cf. Acts 20:7). However Sunday worship has its roots in tradition rather than commandment.

The disciples were still meeting behind closed doors because they feared the Jewish authorities (cf. John 20:19). Jesus again materialized in the presence of these disciples as He had a week earlier (John 20:19). He also repeated His benediction (John 20:21). Perhaps Jesus did these things because the disciples had told Thomas that He had appeared this way and had said these things. This would have bolstered Thomas’ faith.