Exodus 22:20 prescribes death ('utterly destroyed') for anyone who sacrifices to a god other than the LORD.

This law is embedded in Israel's covenant/theocratic constitution, whose legal form draws directly on the ANE suzerain-vassal treaty structure (documented extensively by Meredith Kline and Kenneth Kitchen in their studies of Hittite treaty parallels to the Sinai covenant). Within that framework, sacrificing to another god after Israel's national covenant oath to YHWH ('I am the LORD who brought you out of the land of Egypt, out of the house of slavery,' Ex 20:2) functions structurally like treason against a sovereign to whom the nation owes its very existence and deliverance — analogous, though not identical, to modern states criminalizing treason against the state. This is civil/theocratic law specific to the unique covenant-nation of Israel, not a transcultural mandate to execute non-believers generally. Crucially, the New Testament deliberately does not carry this civil-enforcement model forward: Jesus rebukes his disciples for wanting to call down fire on an unreceptive Samaritan village (Luke 9:54-55), the church is instructed to render to Caesar the sword-bearing civil authority (Rom 13:1-4) while itself wielding only spiritual weapons (2 Cor 10:4), and there is no apostolic command anywhere in the New Testament to execute apostates or unbelievers.

Israel functioned as a unique redemptive-historical nation whose civil law encoded the first commandment because the nation's corporate identity was constituted as a worshiping covenant community bound by treaty to its divine King; the church age deliberately does not replicate this civil-enforcement model, consistent with the classical Reformed distinction between the moral law (perpetual) and Israel's judicial law (expired with the Israelite state, WCF 19.4).