You are misreading Barnabas and reinterpreting his words apart from the historical setting.
Jesus rose on the first day of the week, which Barnabas also refers to as "the eigth day". Only historical revisionists will find the ECF teaching that Jesus rose from the dead on the last day of the week. He did not. He rose on the first day, and the church universal has always recognized this fact by establishing Christian worship on the first day according to the tradition of the apostles as recorded in Scripture.
This is where most of your false doctrine originates. You cannot find any scripture that will substantiate this claim. It is spurious and illogical.... and can be scripturally proved to be in error.