'Letters' in the Bible

And Hezekiah sent to all Israel and Judah, and wrote letters also to Ephraim and Manasseh, that they should come to the house of the LORD at Jerusalem, to keep the passover unto the LORD God of Israel.

So the posts went with the letters from the king and his princes throughout all Israel and Judah, and according to the commandment of the king, saying, Ye children of Israel, turn again unto the LORD God of Abraham, Isaac, and Israel, and he will return to the remnant of you, that are escaped out of the hand of the kings of Assyria.

He wrote also letters to rail on the LORD God of Israel, and to speak against him, saying, As the gods of the nations of other lands have not delivered their people out of mine hand, so shall not the God of Hezekiah deliver his people out of mine hand.