An honest God is the noblest work of man.

Robert Green Ingersoll (1833-1899) American lawyer, freethinker, orator

Lecture (1872-01-29), “The Gods,” epigraph, Fairbury Hall, Fairbury, Illinois
    (Source)

First given on the 135th birthday of Thomas Paine. Collected in The Gods and Other Lectures (1876).

See Pope and Butler.