“The body is the servant of the mind. It obeys the operations of the mind, whether they be deliberately chosen or automatically expressed.”

Source: Dune

Voltaire (1916)
Context: Voltaire was not the first or last man to convert a prison into a hall of fame. A prison is confining to the body, but whether it affects the mind, depends entirely upon the mind.
It was while in prison that he changed his name from the one his father gave him — Arouet — to the one he has made famous throughout all time — Voltaire. He said, "I was very unlucky under my first name. I want to see if this one will succeed any better."

Commonly quoted on the internet, and also in recent books such as Planetary Survival Manual by Matthew Stein (2000), p. 51.
Stein's book is the earliest published source located with that precise version of the quote, but the quote can be found in earlier Usenet posts such as this one from 1995 http://groups.google.com/group/rec.arts.ascii/msg/d9f6ec3887950a0d?hl=en, and other published variants of the quote using the words "sacred gift" can be found earlier. A Google Books search http://books.google.com/advanced_book_search?q=%22sacred+gift%22+einstein with the date range restricted to 1900-1990 shows only a handful in the 1980s and 1970s, and several of them attribute it to The Metaphoric Mind by Bob Samples (1976), which also seems to be the earliest published variant. Samples does not provide an exact quote, but writes on p. 26: "Albert Einstein called the intuitive or metaphoric mind a sacred gift. He added that the rational mind was a faithful servant. It is paradoxical that in the context of modern life we have begun to worship the servant and defile the divine." It seems as if the last sentence about worshipping the servant is just Samples' own comment (though in later variants it became part of the supposed quote), while the earlier sentences only paraphrase something that Samples claims Einstein to have said. Einstein had many quotes about the value of intuition and imagination, but the specific word "gift" can be found in a comment remembered by János Plesch in the section Attributed in posthumous publications, "When I examine myself and my methods of thought I come to the conclusion that the gift of fantasy has meant more to me than my talent for absorbing positive knowledge." So, Bob Samples might have been paraphrasing that comment. Likewise Einstein had a number of quotes about the intellect being secondary to intuition, but the language of the intellect "serving" can be found in a quote from the Out of My Later Years (1950) section, "And certainly we should take care not to make the intellect our god; it has, of course, powerful muscles, but no personality. It cannot lead, it can only serve; and it is not fastidious in its choice of a leader."
Misattributed

The lecture in Ashland, Oregon (8th of July 2005)

Source: Hamlet

Source: Battlefield of the Mind: Winning the Battle in Your Mind

Un Art de Vivre (The Art of Living) (1939), The Art of Loving