The body of a rock

This is recorded in the Terao Ka Ki, the chronicle of the house of Terao. Once, a lord asked Musashi "What is this 'Body of a rock'?" Musashi replied, "Please summon my pupil Terao Ryuma Suke." When Teruo appeared, Musashi ordered him to kill himself by cutting his abdomen. Just as Terao was about to make the cut, Musashi restrained him and said to the lord, "This is the 'Body of a Rock'".