The Nature of the Case
First, the person in view is a not a small child but a grown "son." The Hebrew term for "son" (ben) employed here is indefinite. It is sometimes used of children of both sexes (Ex. 21:5) but most often of the male offspring of parents, and that is clearly the sense in this text. Of itself, the word "son" does not give any indication of age. It can refer to a child or a young man (cf. 1 Sam. 4:4; 19:1; 1 Kings 1:33); age must be determined from the context.
In this case, the son in view is not a child, for the sins brought forth in testimony to show his contumacious manner are gluttony and drunkenness (v. 20); hardly the sins of the average 6 or 10 year old. The case also indicates that the parents have tried to restrain their son, but all their efforts have failed (vv. 18, 20); specifying that he is physically beyond their control. Furthermore, the parents bring their son to the magistrates to judge the matter (v. 19); hence, the son would have opportunity to speak on his own behalf. All of this indicates that the "son" in question is no mere child but, rather, a young man at least in his middle teens or older. As Wright observes, "The law is not talking about naughty children but about seriously delinquent young adults."3
Second, the problems associated with this son are severe. This is not the case of a child who has failed to do his chores, spoken back to his parents, or even committed a serious act of disobedience, but of a son of dissolute character who is in full rebellion to the authority of his parents--he holds them and their word in contempt. The text says that the son is "stubborn" and "rebellious" (vv. 18, 20). Both of these descriptive terms are active participles thus indicating habitual action. The son does not display a stubborn streak now and then, or act rebelliously from time to time, but is continuously stubborn and rebellious.
The word "stubborn" refers to one who is obstinate in their resistance to authority. It is used in the Old Testament of a wild untamed heifer (Hos. 4:16), of an immoral woman who has cast off restraint and indulges in lust (Prov. 7:11), and of Israel as a stubborn people who would not submit to God's authority (Ps. 78:8; Isa. 1:23).
The word "rebellious" means, literally, to strike or lash, and is used of those who contend against authority and refuse to heed their words. The "rebellious" individual lashes out in contempt against those who have authority over them verbally, and perhaps even physically.
In light of this, it is important to note that the Law of the Covenant prescribes death for anyone who strikes his parents (Ex. 21:15) or curses his parents (Ex. 21:17). There is, therefore, reason to suppose that the son in this case law has broken the Law of the Covenant in one or both of these ways. The parents also describe the character of their son as being a "glutton" and a "drunkard." These sins are put forth as examples of a life lived without restraint.
In the case of such rebellion and riotous living, and after all attempts at discipline and control have failed, the parents are to bring their son before the magistrates for judgment. If the magistrates concur in the parents' estimate of the situation, they are to order the men of the city to stone the rebel with stones so that he dies (vv. 20-21). The purpose to be served in the execution of the rebellious son is to "put evil away from among you" and that all will "hear and fear" (v.21).
The Real Meaning
Therefore, the law of Deuteronomy 21:18-21 is not about stoning disobedient children. The Bible does not instruct parents to use stoning in dealing with the rebellious nature and disobedience of their children, but to use the rod and reproof (Prov. 29:15). Children are to be trained from a young age by consistent and loving discipline so that the foolishness that is bound up in them can be driven out (Prov. 22:15), and that they will learn to honor and obey their parents and all those whom God has placed in authority over them.
The case law in discussion does not apply to young children during the formative years, but applies, instead, to a grown son (and by extension to a daughter as well) who, for whatever reason, has rebelled against the authority of his parents and will not profit from any of their discipline nor obey their voice in any thing. It is a case of habitual contempt of parental authority characterized by a young adult living a life without moral restraint who lashes out verbally and/or physically against his mother and father. It is a case where the evil character of the son is apparently set, and there is no reasonable hope of him ever changing.
The kind of rebellion against parental authority described in this case law is called "evil" (v. 21). It is evil because it holds both God and His law (i.e., the command to honor parents) in derision. It is evil because it threatens the very existence of the family, and therefore, of society itself. It is evil because it signals the rejection of all God-ordained authority and leads to civil and ecclesiastical disorder. God considers it such a dangerous evil that it must be extinguished by death at the hands of the civil magistrate.4