The Martyrdom of Isaiah
Illustration in Speculum Humanae Salvationis
Universitäts- und Landesbibliothek Darmstadt, MS 2505, fol. 43r
This prophet's death by sawing is detailed in the 3rd-century Ascension of Isaiah (5:1-14). In the bottom panel a king labeled rex moab, "King of Moab," executes a person. The victim does not have a halo like Isaiah, so the event depicted is probably one of the many instances in which the Moabite kings took up the sword against Israel.
Read more about Isaiah.
Source: ULB Darmstadt via Wikimedia Commons