“Art is not a substitute religion: it is a religion (in the true sense of the word: 'binding back', 'binding' to the unknowable, transcending reason, transcendent being). But the church is no longer adequate as a means of affording experience of the transcendental, and of making religion real – and so art has been transformed from a means into the sole provider of religion: which means religion itself.”

Source: Irrational Man: A Study in Existential Philosophy (1958), Chapter Two, The Encounter With Nothingness, p. 20

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.
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.
Context: Buddhism has the characteristics of what would be expected in a cosmic religion for the future: It transcends a personal God, avoids dogmas and theology; it covers both the natural and the spiritual, and it is based on a religious sense aspiring from the experience of all things, natural and spiritual, as a meaningful unity.

Faith in America speech, 2007

Source: Dictionary of Burning Words of Brilliant Writers (1895), P. 344.

Which Level of God Do You Believe In? (2004)
Context: There are several different meanings of the words "religion" and "spirituality," all of which are important. The whole point about an integral or comprehensive approach is that it must find a way to believably include all of those important meanings in a coherent whole.

Exclusive Interview with Aron Ra – Public Speaker, Atheist Vlogger, and Activist https://conatusnews.com/interview-aron-ra-past-president-atheist-alliance-america/, Conatus News (May 17, 2017)

Ode interview (2009)
Context: A lot of the arguments about religion going on at the moment spring from a rather inept understanding of religious truth … Our notion changed during the early modern period when we became convinced that the only path to any kind of truth was reason. That works beautifully for science but doesn't work so well for the humanities. Religion is really an art form and a struggle to find value and meaning amid the ghastly tragedy of human life.

The Ultimate Source of Meaning, Awake! magazine, october 22, 1980.
Others