Full Idea
If the Divine exists it either has or has not virtue. If it has not it is base and unhappy, which is absurd. But if it has it, there will exist something which is better than God, just as a virtue of a horse is better than the horse itself.
Gist of Idea
God without virtue is absurd, but God's virtues will be better than God
Source
Sextus Empiricus (Against the Physicists (two books) [c.180], I.176)
Book Reference
Sextus Empiricus: 'Against the Physicists/Against the Ethicists', ed/tr. Bury,R.G. [Harvard Loeb 1997], p.91
A Reaction
It is obviously better to think of a virtue as some mode of a thing, rather than as a separate attachment. This is an ontological argument, because it is inferred from the concept of God.