“Bodhicitta is the medicine which revives and gives life to every sentient being who even hears of it.”

1880s, 1880, Letter to Theo (Cuesmes, July 1880)

Les médecins administrent des médicaments dont ils savent très peu, à des malades dont ils savent moins, pour guérir des maladies dont ils ne savent rien.
This attribution to Voltaire appears in Strauss' Familiar Medical Quotations (1968), p. 394, and in publications as early as 1956 http://books.google.pt/books?id=lCtCAQAAIAAJ&q=%22Doctors+are+men+who+prescribe+medicine+of%22&dq=%22Doctors+are+men+who+prescribe+medicine+of%22&hl=pt-PT&sa=X&ei=mbnWUsvDIfTB7Aaw_YD4Dw&redir_esc=y; the quotation in French does not, however, appear to be original, and is probably a relatively modern invention, only quoted in recent (21st century) published works, which attribute it to "Voltaire" without citing any source.
Attributed

Attributed

Kulturphilosophie (1923), Vol. 2 : Civilization and Ethics

Foreword
All Else Is Bondage : Non-Volitional Living (1964)
Context: There seems never to have been a time at which sentient beings have not escaped from the dungeon of individuality. In the East liberation was elaborated into a fine art, but it may be doubted whether more people made their escape from solitary confinement outside the organised religions than by means of them.
In the West reintegration was sporadic, but in recent years it has become a widespread preoccupation. Unfortunately its technical dependence on oriental literature — sometimes translated by scholars whose knowledge of the language was greater than their understanding of the subject — has proved a barrier which rendered full comprehension laborious and exceedingly long. Therefore it appears to be essential that such teaching as may be transmissible shall be given in a modern idiom and in accordance with our own processes of thought. But this presentation can never be given by the discursive method to which we are used for the acquisition of conceptual knowledge, for the understanding required is not conceptual and therefore is not knowledge.
This may account for the extraordinary popularity of such works as the Tao Te Ching, and in a lesser degree for that of the Diamond and Heart Sutras and Padma Sambhava's Knowing the Mind. For despite the accretion of superfluous verbiage in which the essential doctrine of some of the latter has become embedded, their direct pointing at the truth, instead of explaining it, goes straight to the heart of the matter and allows the mind itself to develop its own vision. An elaborately developed thesis must always defeat its own end where this subject matter is concerned, for only indication could produce this understanding, which requires an intuitional faculty, and it could never be acquired wholesale from without.

This attribution to Voltaire appears in Strauss' Familiar Medical Quotations (1968), p. 394, and in publications as early as 1956 http://books.google.pt/books?id=lCtCAQAAIAAJ&q=%22Doctors+are+men+who+prescribe+medicine+of%22&dq=%22Doctors+are+men+who+prescribe+medicine+of%22&hl=pt-PT&sa=X&ei=mbnWUsvDIfTB7Aaw_YD4Dw&redir_esc=y; the quotation in French does not, however, appear to be original, and is probably a relatively modern invention, only quoted in recent (21st century) published works, which attribute it to "Voltaire" without citing any source.
Original: (fr) Les médecins administrent des médicaments dont ils savent très peu, à des malades dont ils savent moins, pour guérir des maladies dont ils ne savent rien.

The Ocean of Theosophy by William Q. Judge (1893), Chapter 1, Theosophy and the Masters

Source: The Zen Teachings of Huang Po (1958), p. 29
Context: All the Buddhas and all sentient beings are nothing but the One Mind, beside which nothing exists. This Mind, which is without beginning, is unborn and indestructible. It is not green nor yellow, and has neither form nor appearance. It does not belong to the categories of things which exist or do not exist, nor can it be thought of in terms of new or old. It is neither long nor short, big nor small, for it transcends all limits, measure, names, traces and comparisons. It is that which you see before you - begin to reason about it and you at once fall into error. It is like the boundless void which cannot be fathomed or measured. The One Mind alone is the Buddha, and there is no distinction between the Buddha and sentient things, but that sentient beings are attached to forms and so seek externally for Buddhahood. By their very seeking they lose it, for that is using the Buddha to seek for the Buddha and using mind to grasp Mind. Even though they do their utmost for a full aeon, they will not be able to attain it. They do not know that, if they put a stop to conceptual thought and forget their anxiety, the Buddha will appear before them, for this Mind is the Buddha and the Buddha is all living beings. It is not the less for being manifested in ordinary beings, nor is it greater for being manifest in the Buddhas.