Where's the fulfillment of Mark 10:39?

In my last post, I referred to how John 21:18-19 lines up well with what other sources report about Peter and Mark's use of Peter as a source. Something similar can be said of the apostle John, but with another element that adds further credibility to what's reported about him.

The Gospel Authors' Witness To Each Other

We often think of the evidence for the authorship of the gospels in terms of internal evidence and external sources of the patristic era, like Papias and Irenaeus. But we should also think in terms of the testimony of earlier sources, including the evidence the gospel authors provide for each other.