“In the mystic traditions of the different religions we have a remarkable unity of spirit.”

Words of Sarvepalli Radhakrishnan, quoted by Haile Selassie in an address http://www.jah-rastafari.com/selassie-words/show-jah-word.asp?word_id=radhakrishan during the Indian President's state visit to Ethiopia (13 October 1965), quoted in Foreign Affairs Record Vol. 11-12 (1965-1966) by India Ministry of External Affairs, p. 266; Radhakrishnan is also quoted as having made these remarks in The Visva-Bharati Quarterly Vol. 5 (1939-1940)

As quoted in The Private Albert Einstein (1992) by Peter A. Bucky and Allen G. Weakland, p. 86
Attributed in posthumous publications

Introduction
On the Kabbalah and Its Symbolism (1960)
Context: The Kabbalah, literally 'tradition,' that is, the tradition of things divine, is the sum of Jewish mysticism. It has had a long history and for centuries has exerted a profound influence on those among the Jewish people who were eager to gain a deeper understanding of the traditional forms and conceptions of Judaism. The literary production of the Kabbalists, more intensive in certain periods than in others, has been stored up in an impressive number of books, many of them dating back to the late Middle Ages. For many centuries the chief literary work of this movement, the Zohar, or 'Book of Splendor,' was widely revered as a sacred text of unquestionable value, and in certain Jewish communities it enjoys such esteem to this day.

Our Christ : The Revolt of the Mystical Genius (1921)
Context: In point of fact there are two kinds sorts of mysticism, differing from one another as the ranting of drunkards from the language of illumined spirits. There is the muddled, stammering mysticism, and there is the mysticism luminous with truly ultimate ideas. On the one hand there are the empty dimness and darkness, the barren, chilling sentimentalism and mental debauchery, the foolishly grimacing but rigid phantasms of the Cabbala, of occultism, mysteriosophy and theosophy. We cannot draw too sharp a dividing line between these and the brightness, the simple sincerity, and healthy, rejuvenating strength of genuine mysticism, which takes the most precious gems from philosophy's treasure chest and displays them in the beauty of its own setting. Mysticism is in complete accord with the result, with the sum of philosophy. In fact, mysticism is precisely the sum and the soul of philosophy, in the form of that rapturous, passionate outpouring of love.... We are concerned with an understanding of this serious mysticism, and its meaning could be stated in three words... godlessness... freedom from the world... blessedness of soul.

When the divine heat of love has drawn out all the moisture, heaviness, unfitness, then this holy food plunges such a one into the life of God. As Our Lord himself said to St Augustine, "I am the food of the strong: believe and feast on me. You will not change me into yourself; rather you will be changed into me".
Sermons, From Our Daily Bread

The Divine Commodity: Discovering A Faith Beyond Consumer Christianity (2009, Zondervan)

Autobiography (1936; 1949; 1958)
Context: Religion merges into mysticism and metaphysics and philosophy. There have been great mystics, attractive figures, who cannot easily be disposed of as self-deluded fools. Yet, mysticism (in the narrow sense of the word) irritates me; it appears to be vague and soft and flabby, not a rigorous discipline of the mind but a surrender of mental faculties and living in a sea of emotional experience. The experience may lead occasionally to some insight into inner and less obvious processes, but it is also likely to lead to self-delusion. <!-- p. 14 (1946)

Source: Pranab Mukherjee "Speech by the President of India, Shri Pranab Mukherjee at the concluding function of the centenary celebrations of the former President of India, Dr. Neelam Sanjeeva Reddy"