Full Idea
If it were not morally good and just in its own nature before any positive command of God, that God should be obeyed by his creatures, the bare will of God himself could not beget any obligation upon anyone.
Gist of Idea
The requirement that God must be obeyed must precede any authority of God's commands
Source
Ralph Cudworth (On Eternal and Immutable Morality [1688], Ch.II.3)
Book Reference
'British Moralists 1650-1800 Vol. 1', ed/tr. Raphael,D.D. [Hackett 1991], p.109
A Reaction
This strikes me as a self-evident truth, and a big problem for anyone who wants to make God the source of morality. You don't have to accept anyone's authority just because they are powerful or clever (though they do bestow a certain natural authority!).