John Gill Commentary 1 Kings 12:15

"So the king hearkened not unto the people; for it was a thing brought about of Jehovah, that he might establish his word, which Jehovah spake by Ahijah the Shilonite to Jeroboam the son of Nebat." — 1 Kings 12:15 (ASV)

Wherefore the king hearkened not unto the people
To lessen their taxes, and ease them of their burdens, as they desired:

for the cause was from the Lord ;
it was according to his will and appointment; the defection of the people was willed by the Lord, and various things in Providence turned up to alienate their minds from Rehoboam, and dispose them to a revolt from him in favour of Jeroboam; and the Lord suffered the counsellors of Rehoboam to give him the advice they did, and gave him up to the folly of his own heart to take it:

that he might perform his saying, which the Lord spoke to Ahijah
the Shilonite unto Jeroboam the son of Nebat ;
see (1 Kings 11:29–39) .