Charles Ellicott Commentary Esther 2:23

"And when inquisition was made of the matter, and it was found to be so, they were both hanged on a tree: and it was written in the book of the chronicles before the king." — Esther 2:23 (ASV)

Hanged on a tree. —They were crucified; a common punishment among the Persians, especially for rebels (Herodotus iii. 120, 125, 159, etc.). The dead body of Leonidas was crucified by Xerxes’ orders after the desperate stand at Thermopylæ.

Book of the chronicles. —A sleepless night for Xerxes accidentally brought this matter, after it had been forgotten, to the king’s mind. Herodotus often refers to these Persian Chronicles (vii. 100; viii. 85, 90).