Second it is useful and necessary that in our invocation of God we know what God we are invoking—that true God with whom we have entered into a covenant of faith, who has testified to us in an eternal covenant that He will be our God, and who has sealed that to us with the seal of baptism. This is so that the we might distinguish our invocation from that o f the pagans, the Turks, and such like, who invoke gods that are really not gods at all but fabrications by the father of lies. For it is in no way tolerable to God that any fellowship with false deities hinder His covenant partners in their invocation and worship, s the Holy Spirit eloquently proclaims in 2 Corinthians 6:14–15. The apostle also sets before our eyes the magnitude of this danger—unless we cling to the living God, whose covenant partners we are, by the true of obedience of faith, and wholly abstain from all idolatrous worship and invocation—in 1 Corinthians 10: [20–21]: “The things which the Gentiles sacrifice they sacrifice to demons and not to God, and I do not want you to have fellowship with demons. You cannot drink the cup of the Lord and the cup of demons; you cannot partake of the Lord’s Table and the table of demons.” For κοινωνιαν with the table demons with be followed also by κοινωνια in eternal punishment (Rev. 14:9–12; Luke 11:49–52).
Caspar OIevianus, An Exposition of the Apostles’ Creed, trans. Lyle D. Bierma, Classic Reformed Theology, ed. R. Scott Clark (Grand Rapids: Reformation Heritage Books, 2009), 38–39.