JASAD meant the incompetent son and crown prince of Hazrat Sulaimam a.s.
Please see QXP below.
34:14 When We decreed death for him, nothing showed his death to the wild tribes until a creature of the earth ate away the strength he had mustered. (The incompetent successor Rehoboam destroyed the kingdom.) When the power base fell, the wild tribes rebelled regretting that they should not have suffered the humiliating punishment only if they knew the unseen (that the new king was unjust and weak). [‘Daabba-tul-ardh’ = Creature of the earth was the highly incompetent Rehoboam, son of Solomon 38:34. Historically, ten of the Israelite Tribes also broke away from the kingdom at that point]
38:34 We passed Solomon through difficult times by granting him a very incompetent (son) to succeed him to his throne. Yet, he turned to Us as always. ['Jasad' = A mere body. His son, the crown prince Rehoboam was a hopeless presence (34:14). Until that point in history, the kingdom of Israel was inherited and ruled by the generations of Prophet Jacob]