Judges 8:16

‘ And he took the elders of the city, and thorns of the wilderness, and briers, and with them he taught the men of Succoth.'

The words are expressive. They were taught what it meant to breach the covenant, with thorns and briers, probably by a severe beating. It may be that he spared their lives for he exacted the punishment that he had first promised and no more (verse 7).