Jeremiah 32:10

And I subscribed the deed The following will explain the particulars of Jeremiah's action as given here and in the next vv. "Contracts stamped upon clay tablets have been found in Babylonia, enclosed in an envelope of clay, on the outside of which an exact duplicate of the contract was impressed (see an illustration in Maspero, The Dawn of Civilization, p. 732): if in course of time any disagreement arose, and it was suspected that the outside text had been tampered with, the envelope was broken in the presence of witnesses to see if the inside text agreed with it or not. Earthen jars containing such duplicate contracts have been excavated at Nippur (Peters, Nippur; II. 198)." Dr. ad loc. See further in Johns, Babylonian and Assyrian Laws, Contracts, and Letters, pp. 10 f.

sealed it not in our sense of adding a seal to a signature ("under one's hand and seal"), but sealed up, closed securely.