Judah’s treatment of Adoni-bezek is often considered an application of the law of lex talionis, an eye for an eye and a tooth for a tooth.
But this is not what God’s people should have done. This action clearly shows that the Israelites were starting to act like Canaanites, for it was exactly how Adoni-bezek treated those he defeated. The Israelites were supposed to put all the Canaanites to death (Deuteronomy 7:1–2; Deuteronomy 20:16–17), but they chose rather to chop off the king's toes and thumbs. The Israelites were not yet engaged in all out idolatry or dwelling with the Canaanites peacefully, but we can find seeds of the sin that would become prominent as this book progresses.1
6 Adoni-bezek fled, but they pursued him and caught him and cut off his thumbs and his big toes.