#To where did Hezekiah send messengers and to whom did he write letters?

Hezekiah sent messengers to all of Israel and Judah, and wrote letters to Ephraim and Manasseh. [30:1]

#What did Hezekiah's message tell them?

The message told them they should come to Jerusalem to the house of Yahweh to celebrate the Passover. [30:1]