Before proceeding to the next point, it may be well for us to see whether we do not accept with approval the saying, “No man can serve two masters,” with the addition, “for either he will hate the one, and love the other; or else he will hold to the one, and despise the other,” and further, “You cannot serve God and mammon.” The defence of this passage will lead us to a deeper and more searching inquiry into the meaning and application of the words “gods” and “lords.” Divine Scripture teaches us that there is “a great Lord above all gods.” And by this name “gods” we are not to understand the objects of heathen worship (for we know that “all the gods of the heathen are demons”), but the gods mentioned by the prophets as forming an assembly, whom God “judges,” and to each of whom He assigns his proper work.
For “God stands in the assembly of the gods: He judges among the gods.” For “God is Lord of gods,” who by His Son “has called the earth from the rising of the sun unto the going down thereof.” We are also commanded to “give thanks to the God of gods.” Moreover, we are taught that “God is not the God of the dead, but of the living.” Nor are these the only passages to this effect; but there are very many others.
Source: Against Celsus (New Advent)