A set of 21 inscribed pottery shards (ostraca) found in 1935 at the gate of Lachish — letters and military reports written in paleo-Hebrew during the final weeks before Nebuchadnezzar's army overran the city in 586 BC. Letter 4 famously reports "we are watching for the signal-fires of Lachish according to all the signs my lord has given, because we cannot see Azekah."
Why this matters
Matches Jeremiah 34:7 verbatim: only Lachish and Azekah remained of Judah's fortified cities. The ostraca are the last surviving Hebrew documents from the kingdom of Judah before the exile.
Scripture references
Jeremiah 34:7Jeremiah 38:1-62 Kings 25:1-7
Location
Tel Lachish, Israel