Full Idea
By this method of reasoning you renounce all claim to infinity in any of the attributes of the Deity. The cause ought to be proportional to the effect, and the effect, so far as it falls under our cognizance, is not infinite.
Gist of Idea
If the divine cause is proportional to its effects, the effects are finite, so the Deity cannot be infinite
Source
David Hume (Dialogues Concerning Natural Religion [1751], Part 5)
Book Reference
'The Existence of God', ed/tr. Hick,John [Macmillan 1964], p.105
A Reaction
You cannot deny that the Deity MAY be infinite, be only accept that your evidence is not enough to prove it. But if nothing infinite has been observed, it is a reasonable provisional inference that nothing infinite exists.