The Seven Stages of Purification!
Following the Noble 8-fold Way the mind is purified in 7 stages:
1: Purification of Morality (sīla-visuddhii).
2: Purification of Mind (citta-visuddhi).
3: Purification of View (ditthi-visuddhi).
4: Purification by Overcoming Doubt (kankhā-vitarana-visuddhi).
5: Purification by knowledge & vision of what is Path and Not-Path.
6: Purification by knowledge and vision of Progress on the Path.
7: Purification of Knowledge and Vision (ñānadassana-visuddhi).
The classic text is MN 24 Ratha-vinita Sutta: The Relay Chariots:
http://www.accesstoinsight.org/tipitaka/mn/mn.024.than.html
And for a complete account of Full Mental Purification:
The Path of Purification: Visuddhimagga." by the great explainer
Buddhaghosa in 5th century AC well translated by Bhikkhu Ñānamoli.
http://www.pariyatti.org/Bookstore/productdetails.cfm?sku=771100
More on these 7 stages of mental purity:
http://What-Buddha-Said.net/drops/II/The_purpose_of_purification.htm
http://What-Buddha-Said.net/drops/Levels_of_Leaving_Behind.htm
http://What-Buddha-Said.net/drops/II/The_7_Purifications.htm
http://What-Buddha-Said.net/drops/9_Stillings.htm
http://www.pariyatti.com/book.cgi?prod_id=404506
