Albert Barnes Commentary 1 Kings 12:8

"But he forsook the counsel of the old men which they had given him, and took counsel with the young men that were grown up with him, that stood before him." — 1 Kings 12:8 (ASV)

The age of Rehoboam at his accession is an interesting and difficult question. According to the formal statement in 1 Kings 14:21 and 2 Chronicles 12:13, he had reached the mature age of forty-one and would therefore be unable to plead youth as an excuse for his conduct. The general narrative, however, seems to assume he was quite a young man (compare 2 Chronicles 13:7).

Perhaps the best way to resolve this difficulty is to read “twenty-one” instead of “forty-one” in the referenced texts. This type of corruption could easily have occurred if letters were used for numerals.