Pure Religion is a term used by Tathagata in The Book of the Great Decease to refer to his attempt to provide a pure, powerful, and successful Authentic Spirituality.
Authentic Spirituality > Cosmic Religion, Identity Consistent Spirituality, Mysticism, Perennial Philosophy, Positive Religion, Progressive Spirituality, Pure Religion, Right Path, The Path, The Way, True Path
A quote from The Book of the Great Decease lays this all out.
"I shall not die, O Evil One! until not only the brethren and sisters of the order, but also the lay-disciples of either sex shall have become true hearers, wise and well-trained, ready and learned, versed in the Scriptures, fulfilling all the greater and the lesser duties, correct in life, walking according to the precepts-until they, having thus themselves learned the doctrine, shall be able to tell others of it, preach it, make it known, establish it, open it, minutely explain it and make it clear-until they, when others start vain doctrine, shall be able by the truth to vanquish and refute it, and so to spread the wonder-working truth abroad! '"I shall not die until this pure religion of mine shall have become successful, prosperous, wide-spread, and popular in all its full extent-until, in a word, it shall have been well proclaimed among men!"
Also note, Tathagata is aware of the existence of false systems, false teachings, inauthentic spiritualities. When asked whether certain people who claim to have "thoroughly understood things" really do, Tathagata says:
Void are the systems of other teachers-void of true saints. But in this one, Subhadda, may the brethren live the perfect life, that the world be not bereft of those who have reached the highest fruit.'