Wonderful teachings from the Surangama Sutra. In the following passage, the Buddha explained the two fundamental points of spiritual practice.
Ananda,.... you should see clearly if the cause ground (used as) a point of departure and its fruit-ground (i.e. realization) are compatible or not. Ananda, if you use your worldly mind as a causal point of departure, you will fail in your search for the Buddha Vehicle which is beyond birth and death. Therefore, you should inquire into all the creations (of the mind) which in this material world are subject to change and destruction. Ananda, which one of them does not decay? Yet you have never heard that space can perish. Why? Because it is not a created thing. What is the second decisive factor? In your determination to develop the Bodhi Mind and to advance boldly along the Bodhisattva Path by relinquishing everything worldly, you should look closely into the origin of klesha (affliction), caused by your basic ignorance and developing discrimination, and see who creates and endures them. Ananda, in your cultivation of Bodhi, if you do not inquire into the root of klesha, you will never know (how and) where the organs and sense data are turned upside down. If you fail to understand this, how can you overcome them to win the Tathàgata stage?
So what kind of worldly mind are we bringing into our churches and temples, our meditation and charity? Take away all the external forms and appearances and look what's left there. If you can see through the worldly mind, and there is the one who creates and endures our suffering - only this can truly liberate us.