דברי הימים ב יג:ז פירוש: רש״י

And there gathered to him worthless wicked.

and they overwhelmed Rehoboam the son of Solomon and Rehoboam was young and soft-hearted and since they found in him humility and soft- heartedness, they overwhelmed him.

young - Heb. נַעַר. Although he was forty-one years old when he reigned, he is called a youth (נַעַר), as I explained above (I Chron. 22:5) in regards to Solomon.