Foundation nail dedicated by Entemena, king of Lagash, to the god of Bad-Tibira, about the peace treaty concluded between Lagash and Umma. Extract from the inscription: “Those were the days when Entemena, ruler of Lagash, and Lugal-kinishe-dudu, ruler of Umma, concluded a treaty of fraternity". This text is the oldest diplomatic document known. Found in Telloh, ancient Girsu, ca. 2400 BC.
Reed Enger, "Clay Nails - A Treaty of Fraternity," in Obelisk Art History, Published May 14, 2015; last modified July 09, 2018, http://arthistoryproject.com/timeline/the-ancient-world/mesopotamia/clay-nails-a-treaty-of-fraternity/.