Barnabas- The author is not known, but an important statement is made in the epistle concerning its dating.
Furthermore, again he says: "Behold, those who tore down this temple will build it themselves." This is happening now. For because they went to war, it was torn down by their enemies, and now the very servants of their enemies will rebuild it. Again, it was revealed that the city and the temple and the people of Israel were destined to be handed over. For the Scripture says, "And it will happen in the last days that the Lord will hand over the sheep of the pasture and the sheepfold and their watchtower to destruction." And it happened just as the Lord said. [16:3-5]
Evidently this was written after A.D. 70 when the city and temple were destroyed by the Romans but sometime before it was to be rebuilt by Hadrian after the second Jewish revolt which began in 132.
It is noteworthy that there is no mention made in the epistle of the approaching return of Christ nor the gathering together of His saints into heaven. One might gather from this silence that the Return was no longer their hope, having already occurred.
Howbeit, there is another passage in Barnabas' epistle that we should be especially attentive to.
This is why we spend the eighth day in celebration, the day on which Jesus both arose from the dead and, after appearing again, ascended into heaven. [15:9]
Here is a great example of the second generation of believers not knowing the details surrounding the life, death, resurrection and return of our Lord. And beyond that, how the following generations have accepted what the Apostolic Fathers wrote over and above what the Scripture plainly teaches.
To anyone who has taken the time to study the Gospel accounts of the resurrection of our Lord, un-tethered from Church Tradition, he can't fail to see that when Mary came to the tomb before sunrise, which would have began the eighth day, Yeshua had already been risen (MATTHEW 28:1). He rose late on Saturday, the Sabbath, not Sunday, the eighth day of the week. (see Resurrection Sunday?)
Howbeit, in this epistle Barnabas writes that Yeshua arose on Sunday which nearly every commentator since has blindly accepted as fact. So do we accept, believe and perpetuate the Scripture; or do we accept, believe and perpetuate what Barnabas is said to have written?
Yet the question that we should be asking, is, How could Barnabas write and others accept this grave error? How could they not know on which day of the week Yeshua arose? Barnabas wrote, at the furthest, only seventy years after the book of ACTS closes and if tradition is right, only twenty or thirty years after the death of John the Apostle. One has a hard time imagining how they could have not known this important detail.
The only answer that makes sense and seems logical, is that Barnabas and his readers didn't know what day Yeshua arose because there was no one around to tell them. They very possibly only had one or two Gospels at their disposal and as only MATTHEW and LUKE specifically say that He had arisen before sunrise, they evidently assumed that He had risen on Sunday.