For out of prison he cometh to reign; whereas also he that is born in his kingdom becometh poor.
For out of prison he (the poor and wise child) cometh to reign. Solomon uses this phrase of a supposed case-e.g., Joseph raised from a dungeon to be lord of Egypt. His words are at the same time so framed by the Holy Spirit that they answer virtually to Jeroboam, who fled, to escape a "prison" and death from Solomon, to Shishak of Egypt (1 Kings 11:40). This unconscious presaging of his own doom, and that of Rehoboam, constitutes the irony. David's elevation from poverty and exile, under Saul (which may have been before Solomon's mind), had so far their counterpart in that of Jeroboam.
Whereas also (he that is) born in his kingdom becometh poor - whereas the old king (in the person of his son. "the second child," Ecclesiastes 4:15), who came to the kingdom by birth (by hereditary right) becometh poor. So the Vulgate.