Midrasch zu Schemuel II 19:1

Rabbi José said: There are seven doors to Gehinnom. Absalom entered as far as the fifth door, and David heard (thereof), and began to weep, to lament, and to mourn, and he called Absalom! My son! five times, My son, my son, my son! "And the king was much moved, and he went up to the chamber over the gate, and wept: and as he went, thus he said, O my son Absalom, my son, my son Absalom! would God I had died for thee, O Absalom, my son, my son!" (2 Sam. 18:33). And they brought him back from the five doors of Gehinnom, and he began to praise and laud and to glorify his Creator, saying: "Shew me a token for good; that they which hate me may see it, and be ashamed: because thou, Lord, hast helped me, and comforted me" (Ps. 86:17). "Thou hast helped me" out of the war of Absalom, and "thou hast comforted me" in my mourning for him.