http://www.newadvent.org/cathen/06608b.htm
Neither in the Old or New Testament do we find any elaborate argumentation devoted to proving that God exists. This truth is rather taken for granted, as being something, for example, that only the fool will deny in his heart [Psalm 13:1 and 52:1]; and argumentation, when resorted to, is directed chiefly against polytheism and idolatry. But in several passages we have a cursory appeal to some phase of the general cosmological argument: v.g. Psalm 18:1 and 93:5 sqq., Isaiah 41:26 sqq.; II Mach., vii, 28, etc.; and in some few others — Wis. xiii, 1-9; Rom., i, 18,20 — the argument is presented in a philosophical way, and men who reason rightly are held to be inexcusable for failing to recognize and worship the one true God, the Author and Ruler of the universe.
These two latter texts merit more than passing attention. Wis., xiii, 1-9 reads:
But all men are vain in whom there is not the knowledge of God: and who by these good things that are seen, could not understand him that is, neither by attending to the works have acknowledged who was the workman: but have imagined either the fire, or the wind, or the swift air or the circle of the stars, or the great water, or the sun and moon, to be the gods that rule the world. With whose beauty, if they, being delighted, took them to be gods: let them know how much the Lord of them is more beautiful than they: for the first author of beauty made all those things. Or if they admired their power and effects, let them understand by them that he that made them, is mightier than they: for by the greatness of the beauty, and of the creature, the creator of them may be seen, so as to be known thereby. But yet as to these they are less to be blamed. For they perhaps err, seeking God, and desirous to find him. For being conversant among his works, they search: and they are persuaded that the things are good which are seen. But then again they are not to be pardoned. For if they were able to know so much as to make a judgment of the world: how did they not more easily find out the Lord thereof?