Full Idea
It is not to be understood that the assumption of the existence of God is necessary as a ground for all obligation in general (for this rests, as has been shown, solely on the autonomy of reason itself).
Gist of Idea
Obligation does not rest on the existence of God, but on the autonomy of reason
Source
Immanuel Kant (Critique of Practical Reason [1788], I.II.II.V)
Book Reference
Kant,Immanuel: 'Critique of Practical Reason (Third edition)', ed/tr. Beck,Lewis White [Library of Liberal Arts 1993], p.132
A Reaction
This shows that Kant agrees with Plato about the Euthyphro Question - that is, they both think that morality is logically and naturally prior to any gods. I agree. Why would we admire or worship or obey gods if we didn't think they were good?