Jamieson, Fausset and Brown on Deuteronomy 21:18-21

18-21. If a man have a stubborn and rebellious son--A severe law was enacted in this case. But the consent of both parents was required as a prevention of any abuse of it; for it was reasonable to suppose that they would not both agree to a criminal information against their son except from absolute necessity, arising from his inveterate and hopeless wickedness; and, in that view, the law was wise and salutary, as such a person would be a pest and nuisance to society. The punishment was that to which blasphemers were doomed [Le 24:23]; for parents are considered God's representatives and invested with a portion of his authority over their children.