'Letters' in the Bible

Moreover I said to the king, "If it pleases the king, let letters be given me to the governors beyond the River, that they may let me pass through until I come to Judah;

Then I came to the governors beyond the River, and gave them the king's letters. Now the king had sent with me captains of the army and horsemen.

Moreover in those days the nobles of Judah sent many letters to Tobiah, and [the letters] of Tobiah came to them.

Also they spoke of his good deeds before me, and reported my words to him. Tobiah sent letters to put me in fear.