'Letters' in the Bible

Moreover I said unto the king, If it please the king, let letters be given me to the governors beyond the river, that they may convey me over till I come into Judah;

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

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

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