what additional information does elijah provide ishmael and queequeg with respect to captain ahab

A stranger passes Ishmael and Queequeg and asks them whether they have signed the articles, and whether this means that they have signed their souls. He then asks if they have souls at all to sell. The stranger asks if they have met Old Thunder (Captain Ahab). Ishmael says that Captain Ahab is ill, but the strangers says that when Captain Ahab is all right, then his left arm (which he does not have) will be all right. The stranger tells them that Ahab lost his leg. The stranger introduces himself as Elijah, then Ishmael and Queequeg leave him.