“Religious structure often dilutes the spiritual experience.”

The Ageless Wisdom, An Introduction to Humanity's Spiritual Legacy (1996)

The Spiral Staircase: My Climb Out of Darkness (2004)
Context: The one and only test of a valid religious idea, doctrinal statement, spiritual experience, or devotional practice was that it must lead directly to practical compassion. If your understanding of the divine made you kinder, more empathetic, and impelled you to express this sympathy in concrete acts of loving-kindness, this was good theology. But if your notion of God made you unkind, belligerent, cruel, or self-righteous, or if it led you to kill in God's name, it was bad theology. Compassion was the litmus test for the prophets of Israel, for the rabbis of the Talmud, for Jesus, for Paul, and for Muhammad, not to mention Confucius, Lao-tsu, the Buddha, or the sages of the Upanishads.

As quoted in "The Dreams of William Golding", BBC Arena (2012)

These two statements are very similar, widely quoted, and seem to paraphrase some ideas in the essay "Religion and Science" (see below), but neither of the two specific quotes above been properly sourced. Notable Einstein scholars such as John Stachel and Thomas J. McFarlane (author of Buddha and Einstein: The Parallel Sayings) know of this statement but have not found any source for it. Any information on any definite original sources for these is welcome.
This quote does not actually appear in Albert Einstein: The Human Side as is sometimes claimed.
Only two sources from before 1970 can be found on Google Books. The first is The Theosophist: Volume 86 which seems to cover the years 1964 http://books.google.com/books?id=7pLjAAAAMAAJ&q=1964#search_anchor and 1965 http://books.google.com/books?id=7pLjAAAAMAAJ&q=1965#search_anchor. The quote appears attributed to Einstein on p. 255 http://books.google.com/books?id=7pLjAAAAMAAJ&q=%22natural+and+spiritual%22#search_anchor, with the wording given as "The religion of the future will be a cosmic religion. It should transcend a personal God and avoid dogmas and theology. Covering both the natural and the spiritual, it should be based on a religious sense arising from the experience of all things, natural and spiritual, as a meaningful unity. Buddhism answers this description." An identical quote appears on p. 284 http://books.google.com/books?id=YpsfAQAAIAAJ&q=%22dogmas+and+theology%22#search_anchor of The Maha Bodhi: Volume 72 published by the Maha Bodhi Society of India, which seems to contain issues from throughout 1964 http://books.google.com/books?id=YpsfAQAAIAAJ&q=%22volume+72%22#search_anchor.
A number of phrases in the quote are similar to phrases in Einstein's "Religion and Science". Comparing the version of the quote in The Theosophist to the version of "Religion and Science" published in 1930, "a cosmic religion" in the first resembles "the cosmic religious sense" in the second; "transcend a personal God" resembles "does not involve an anthropomorphic idea of God"; "covering both the natural and the spiritual" resembles "revealed in nature and in the world of thought"; "the experience of all things, natural and spiritual, as a meaningful unity" resembles "experience the totality of existence as a unity full of significance"; and "Buddhism answers this description" resembles "The cosmic element is much stronger in Buddhism". These phrases appear in the same order in both cases, and the ones from "Religion and Science" are all from a single paragraph of the essay.
Misattributed
Variant: The religion of the future will be a cosmic religion. It should transcend a personal God and avoid dogmas and theology. Covering both the natural and the spiritual, it should be based on a religious sense arising from the experience of all things, natural and spiritual as a meaningful unity. If there is any religion that would cope with modern scientific needs, it would be Buddhism.

This is attributed to Pierre Teilhard de Chardin in The Joy of Kindness (1993), by Robert J. Furey, p. 138; but it is attributed to G. I. Gurdjieff in Beyond Prophecies and Predictions: Everyone's Guide To The Coming Changes (1993) by Moira Timms, p. 62; neither cite a source. It was widely popularized by Wayne Dyer, who often quotes it in his presentations, crediting it to Chardin, as does Stephen Covey in Living the 7 Habits : Stories of Courage and Inspiration (2000), p. 47. Such statements could be considered paraphrases of Hegel's dictum that matter is spirit fallen into a state of self-otherness. Or any number of thousands of similarly vague quotes by hundreds of predecessors.
Disputed
Variant: We are not human beings on a spiritual journey. We are spiritual beings on a human journey.
Variant: We are not human beings having a spiritual experience; we are spiritual beings having a human experience.

Indian Spirituality and Life (1919)
Context: The highest spirituality indeed moves in a free and wide air far above that lower stage of seeking which is governed by religious form and dogma; it does not easily bear their limitations and, even when it admits, it transcends them; it lives in an experience which to the formal religious mind is unintelligible. But man does not arrive immediately at that highest inner elevation and, if it were demanded from him at once, he would never arrive there. At first he needs lower supports and stages of ascent; he asks for some scaffolding of dogma, worship, image, sign, form, symbol, some indulgence and permission of mixed half-natural motive on which he can stand while he builds up in him the temple of the spirit. Only when the temple is completed, can the supports be removed, the scaffolding disappear. The religious culture which now goes by the name of Hinduism not only fulfilled this purpose, but, unlike certain credal religions, it knew its purpose. It gave itself no name, because it set itself no sectarian limits; it claimed no universal adhesion, asserted no sole infallible dogma, set up no single narrow path or gate of salvation; it was less a creed or cult than a continuously enlarging tradition of the Godward endeavour of the human spirit. An immense many-sided many-staged provision for a spiritual self-building and self-finding, it had some right to speak of itself by the only name it knew, the eternal religion, Sanâtana Dharma. It is only if we have a just and right appreciation of this sense and spirit of Indian religion that we can come to an understanding of the true sense and spirit of Indian culture.

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