How does Sai Baba explain the process of mental purification required for Self-realization?

Chapter 37 illustrates the necessity of purification using the analogy of making ghee from milk. Just as milk must be soured to become buttermilk, churned to yield butter, and heated to become pure ghee, the mind requires a similar process. The text states that without practice, there is no purity of mind, and without that purity, knowledge is difficult to attain. Therefore, diligent practice and purification are essential steps. The state of the mind must become pure for Self-realization to occur, highlighting that this is an active, effortful process.