An English translation:
Princeton, 3. 1. 1954
Dear Mr Gutkind,
Inspired by Brouwer’s repeated suggestion, I read a great deal in your book, and thank you very much for lending it to me ... With regard to the factual attitude to life and to the human community we have a great deal in common. Your personal ideal with its striving for freedom from ego-oriented desires, for making life beautiful and noble, with an emphasis on the purely human element ... unites us as having an “American Attitude.”
Still, without Brouwer’s suggestion I would never have gotten myself to engage intensively with your book because it is written in a language inaccessible to me. The word God is for me nothing more than the expression and product of human weakness, the Bible a collection of honorable, but still purely primitive, legends which are nevertheless pretty childish. No interpretation no matter how subtle can (for me) change this. ... For me the Jewish religion like all other religions is an incarnation of the most childish superstition. And the Jewish people to whom I gladly belong ... have no different quality for me than all other people. As far as my experience goes, they are also no better than other human groups, although they are protected from the worst cancers by a lack of power. Otherwise I cannot see anything “chosen” about them.
In general I find it painful that you claim a privileged position and try to defend it by two walls of pride, an external one as a man and an internal one as a Jew. As a man you claim, so to speak, a dispensation from causality otherwise accepted, as a Jew of monotheism. But a limited causality is no longer a causality at all, as our wonderful Spinoza recognized with all incision...
Now that I have quite openly stated our differences in intellectual convictions it is still clear to me that we are quite close to each other in essential things, i.e. in our evaluation of human behavior ... I think that we would understand each other quite well if we talked about concrete things.
With friendly thanks and best wishes,
The above is taken from the website Letters Of Note
Einstein reinforced this in a letter to J. Dispentiere on 22 March 1954, in which he said:
"It was, of course, a lie what you read about my religious convictions, a lie which is being systematically repeated. I do not believe in a personal God and I have never denied this but have expressed it clearly. If something is in me which can be called religious then it is the unbounded admiration for the structure of the world so far as our science can reveal it." (Source)
Despite this denial, religious apologists continue to claim Einstein was religious. Obviously, it's much safer to claim a dead scientist as one of your own when fewer and fewer living ones are.