All religions emerge from the same root. Therefore, at the base of all religions is a common source, called by many names, but whose true nature is far beyond the confines of any belief, dogma, or theory. Therefore, all genuine scriptures agree with one another.
In order to experience the truth of that common source, we must free the mind from all cages, chains, and bonds, in order for the soul and spirit to rise above all terrestrial and materialistic limitations. In other words, we must study all religions, discard from them what is added (especially by our mind), and resolutely discover what is essential, original, and divine.
The Gnostic tradition studies all the religious and mystical traditions in the world, since Gnosis is the root from which they all flowered.
"In the Gnostic tradition, we have a vast collection of spiritual writings that nourish our efforts to awaken our consciousness. To begin, we have the more than sixty books by Samael Aun Weor, and the hundreds of complementary lectures and talks that he gave. This body of knowledge was given in order to elucidate understanding of the Christian Bible, the Torah, the Zohar, the Bhagavad-Gita, the Germanic Eddas, all the great psychological wisdom hidden in the Greek myths, the Odyssey and the Illiad of Homer, and hundreds of other volumes from our religious and classical heritage. As well, Gnosis is found in the one hundred volumes of Buddhist sutras and in the two hundred volumes of commentaries on those sutras by great masters such as Tsong Khapa and Nagarjuna. Gnosis saturates the Tibetan Tantric tradition and overflows from the teachings of Milarepa, the Dalai Lamas, and many others." - The Purpose of Gnosis
Here are some excerpts from important scriptures, but by no means is this an exhaustive or authoritative list.
"No one can achieve illumination without having been previously purified. Only those that have achieved purification and sanctity can enter into the hall of illumination."