Full Idea
To deduce from reason [Vernunft] the moral element in conduct is blasphemy. In this element there is expressed the better consciousness which lies far above all reason. expresses itself in conduct as holiness, and is the true salvation of the world.
Gist of Idea
To deduce morality from reason is blasphemy, because it is holy, and far above reason
Source
Arthur Schopenhauer (Manuscript remains [1855], I p.47), quoted by Peter B. Lewis - Schopenhauer 3
Book Reference
Lewis, Peter B.: 'Schopenhauer' [Reaktion Books 2012], p.66
A Reaction
Aimed at Kant. Only Plato could inspire a non-religious person to write about morality is such terms. Maybe also the stoic ideal of beautiful deeds (given the supreme value Schopenhauer placed on the arts).