John Gill Commentary 1 Kings 13:34

"And this thing became sin unto the house of Jeroboam, even to cut it off, and to destroy it from off the face of the earth." — 1 Kings 13:34 (ASV)

And this thing became sin unto the house of Jeroboam
All the above things were sins in themselves, as building high places, and putting priests in them, whoever would; but the sense is, that these were the causes of punishment, or of evil things being inflicted on Jeroboam's family; sin is put for the punishment of sin, as it often is:

even to cut it off, and to destroy it from off the face of the earth ;
so that it become utterly extinct; and the next thing we hear of is the sickness and death of his son.