Hume Section 2 OF THE ORIGIN OF IDEAS

"our thoughts or ideas, however compunded or sublime, we always find, that they resolve themselves into such simple ideas as were copied from a precedent feeling or sentiment. Even those ideas, which, at first view, seem the most wide of this origin, are found, upon a nearer scrutiny, to be derived from it."

I think what Hume is saying here is that our thoughts are confined and derived from outward and inward feelings which he calls impressions. He defines impressions as living perceptions(when we hear, see, feel love, hate , desire, or will). He then uses the idea of God as an example. He says that the idea of God comes from the operations of our mind increasing without limit the qualities of goodness and wisdom. He believes that every idea comes from an impression. So I think he is saying that the idea of God comes from the impression of wisdom and goodness because most people believe that God is good and all-knowing.