'Letters' in the Bible

Then I said to the king, "If it is good for the king, let letters be given to me for the governors [in the province] Beyond the River, that they may let me pass until I come to Judah.

I came to the governors of [the province] Beyond the River, and I gave them the letters of the king. Then the king sent troop commanders and horses with me.

Also, in those days the nobles of Judah increasingly sent their letters to Tobiah, and [letters] from Tobiah returned to them.

They also were speaking of his good deeds in my presence, and they were sending my words out to him. Tobiah sent letters to intimidate me.