A 10-year-old Russian boy, Matvei Tcepliaev, recently made an extraordinary discovery in Jerusalem. Working as a volunteer in the Temple Mount Sifting Project, he found a 3,000-year-old seal—engraved limestone about the size of a thimble, with a hole at one end so it could be hung from a string—from the time of King David. The artifact was nestled in the hundreds of tons of earth and rock that had been illegally excavated from below the Temple Mount in the late 1990s by the Muslim Waqf, a trust that retains authority over the contested site. The Temple Mount is sacred ground...