Midrasch zu Schemuel II 18:12

Rabbi Eliezer said: Come and see the integrity and perfection of that man, for he said to Joab, Even if thou wouldst give me gold and silver I would not transgress the king's commands which he commanded thee, as it is said, "And the man said unto Joab, Though I should receive a thousand (pieces of) silver in mine hand" (2 Sam. 18:12). Joab said to him: I beseech thee, show me the place where Absalom is hanging. But he did not consent. Joab began to bend the knee, and to prostrate himself before him, as it is said, "Then said Joab, Shall I not entreat thee in this wise?" (2 Sam. 18:14). Then he took (Joab) by his arm, and showed him the place where Absalom was hanging. Everyone who transgresses the commandment "Honour thy father" is accounted as though he had transgressed the Decalogue. Therefore was (Absalom) pierced by ten spears, as it is said, "And ten young men that bare Joab's armour compassed about and smote Absalom; and slew him" (2 Sam. 18:15).