Midrash su Esdra 8:9

R. Pinchas b. Chama lectured: "What is the meaning of the passage (I Kings 11, 21) And when Hadad heard in Egypt that David slept with his father, and that Joab, the captain of the host died. Why does the passage concerning David say lay and concerning Joab say died? Because David left sons, therefore it says lay, but Joab did not leave any sons, therefore it says died. Did not Joab leave sons? Behold the passage says (Ezra 8, 9) Of the sons of Joah, Obediah, etc. We must therefore explain the above contradiction thus: David who left a son like himself, is referred to as merely lay, but Job did not leave a son resembling himself; therefore he is mentioned as died.