Tonight on The Last Word: President Biden says the U.S. stands "shoulder-to-shoulder" with Israel. Also, Hezbollah and Israeli forces trade fire. And Hamas threatens to execute hostages if Israeli forces bomb civilian houses in Gaza. Matthew Miller, Ronen Bergman, Nicholas Kristof, Ali Velshi, Ali Arouzi, Rick Stengel, Robin Wright and Peter Beinart join Lawrence O'Donnell.