Athanasius of Alexandria

Since God is one, it is ridiculous to suppose that there could be still another "Lord" of heaven and earth in addition to the Lord who is one. There is simply no room for a second Lord of all, if the one true God fills all things in the compass of heaven and earth.

Against the Heathen 6.4 ↗

Ignatius of Antioch

For Moses, the faithful servant of God, when he said, "The Lord thy God is one Lord," and thus proclaimed that there was only one God, did yet forthwith confess also our Lord when he said, "The Lord rained upon Sodom and Gomorrah fire and brimstone from the Lord." And again, "And God said, Let Us make man after our image: and so God made man, after the image of God made He him." And further "In the image of God made He man." And that [the Son of God] was to be made man [Moses shows when] he says, "A prophet shall the Lord raise up …

Epistle of Pseudo-Ignatius to the Antiochians ↗

Cyprian

For both to prophesy and to cast out devils, and to do great acts upon the earth is certainly a sublime and an admirable thing; but one does not attain the kingdom of heaven although he is found in all these things, unless he walks in the observance of the right and just way. The Lord denounces, and says, "Many shall say to me in that day, Lord, Lord, have we not prophesied in Thy name, and in Thy name have cast out devils, and in Thy name done many wonderful works? …

Treatise I. On the Unity of the Church. ↗

Hilary of Poitiers

They employ the confession of One God, for which they appeal to the witness of the Law and the Gospels in the words, Hear, O Israel, the Lord thy God is One. They are well aware of the risks involved, whether their assertion be met by contradiction or passed over in silence; and, whichever happens, they see an opening to promote their heresy. …

On The Trinity 5.1-2 ↗