— Henry Wotton English ambassador 1568 - 1639
Attributed. E.g., Vol 24, Encyclopedia Britannica of Arts, Sciences, and General Literature, page 721 https://books.google.com/books?id=_GlJAAAAYAAJ&pg=PA721&lpg=PA721&dq=truth+wotton+confound+advice&source=bl&ots=-cGk3UDLLj&sig=ltOR1xtI9WFic1JWKiFmIZ8Yce0&hl=en&sa=X&ved=0ahUKEwjVkZCsj-jRAhXCyFQKHTmsCkAQ6AEIODAG#v=onepage&q=truth%20wotton%20confound%20advice&f=false (9th Ed. 1894).
Compare Mark Twain who, in Following the Equator, said "When in doubt, tell the truth" (which is often mis-quoted as containing an additional clause providing "it will confound your enemies and astound your friends").