The Mechanisms of Purifying the Soul

The Quran and Sunnah hints at it, there's nothing explicit, but we have references. When you are worshiping Allah in the privacy of secrecy, that is when your tazqihya begins to develop. The Prophet would pray to hedge you all alone, then after srat al-fajr, he would do a thqah all alone. He said away from any prayer except for Fijle filoum (in the middle of the night) will fortify you like nothing else can.