Shalom friends,

Why do we read the book of Jonah on Yom Kippurim?

The obvious reason, of course, is that it is a message about repentance and HaShem's mercy.

Jonah was a prophet to the northern kingdom (the House of Israel) during the reign of Jeroboam II.  Jonah was sent to Nineveh (c. 760 BCE) with a warning -- repent or be destroyed.  Nineveh, the capital of the Assyrian Empire, was the center of immorality and debauchery.  The reluctant Jonah could not figure out why HaShem would be interested in the fate of a foreign people when the prophet's own people were in spiritual state as low as that of the heathen Assyrians.

HaShem had plans for the Assyrians and he wanted to prepare them for their mission.  Forty years after Jonah's mission to Nineveh HaShem used the Assyrians to remove the House of Israel from the land and to relocate them far to the north.  From there they would eventually be scattered to the far corners of the earth.

For millennia, the Jewish people have awaited the return of the exiles (the Ten Lost Tribes) and the coming of Messiah ben David.

Repentance and HaShem's mercy are a message to House of Israel today.  Return to HaShem and He will return to you.  He will write is Torah in your heart and you will be called "benai El Chai" (sons of the Living G-d). [Hosea 1:10]

Kol tov,
Shomeir