This text in the book of the prophet Jeremiah describes the importance of documents and seals in Judah in the sixth century B.C.
Jeremiah said, “The word of the LORD came to me: Behold, Hanamel the son of Shallum your uncle will come to you and say, ‘Buy my field that is at Anathoth, for the right of redemption by purchase is yours.’ Then Hanamel my cousin came to me in the court of the guard, in accordance with the word of the LORD, and said to me, ‘Buy my field that is at Anathoth in the land of Benjamin, for the right of possession and redemption is yours; buy it for yourself.’ Then I knew that this was the word of the LORD. “And I bought the field at Anathoth from Hanamel my cousin, and weighed out the money to him, seventeen shekels of silver. I signed the deed, sealed it, got witnesses, and weighed the money on scales. Then I took the sealed deed of purchase, containing the terms and conditions and the open copy. ( Jeremiah 32:6-11 ESV. Continue reading in Jeremiah for the full story.)
Important documents were rolled and then tied with string. A small amount of damp clay was placed on the string and the person would impress his seal into the clay. When the impression dried it made a permanent copy of the seal. This was called a bulla (plural is bullae). Both seals and bulla of various biblical characters have been discovered in Israel.
The photo below is of a display at the Hecht Museum at the University of Haifa.
You can find more information about seals and sealing by putting the word seal in the Search Box. Click on the photo for a larger image suitable for use in teaching.