1 Corinthians 8:4

Epistle of Ignatius to the Antiochians

And those very apostles, who said "that there is one God,"[19]

Irenaeus Against Heresies Book III

For though there be that are called gods, whether in heaven or in earth; yet to us there is but one God, the Father, of whom are all things, and we through Him; and one Lord Jesus Christ, by whom are all things, and we by Him."[46]

Clement of Alexandria Stromata Book VI

Such, then, being the case, the Greeks ought by the Law and the Prophets to learn to worship one God only, the only Sovereign; then to be taught by the apostle, "but to us an idol is no, thing in the world,"[305]

Tertullian De Spectaculis

renounced all idols, they are utterly unsuitable. "Not that an idol is anything,"[15]

Tertullian Against Marcion Book V

He introduces his discussion about meats offered to idols with a statement concerning idols (themselves): "We know that an idol is nothing in the world."[316]

Origen Against Celsus Book VIII " In reference to this statement, it would be profitable for us to take up and clearly explain the whole passage of the first Epistle to the Corinthians, in which Paul treats of offerings to idols.[50]

Novation On the Jewish Meats

And when this creature is taken for food, it nourishes the person who so takes it for the demon, not for God, by making him a fellow-guest with the idol, not with Christ, as rightly do the Jews also.[38]

Didache

bear what thou art able; but against that which is sacrificed to idols[71]