I prayed for freedom for twenty years, but received no answer until I prayed with my legs.

Douglass - prayed with my legs - wist_info quote

Frederick Douglass (1817–1895) American abolitionist, orator, writer
(Attributed)

Mentioned frequently as being part of his earlier speeches, but unsourced. Also found as "failed to see the slightest scintillation of an answer until I prayed with my legs."