As stated in the second chapter of the Quran, one of the duties of the Prophet vis-à-vis his contemporaries was “to teach them the Scripture and wisdom, and purify them” (2:129). It is necessary for every believer to purify himself. Without purification, that calibre of personality, which is called in the Quran a God-oriented personality (3:79) cannot be developed. The truth is that purification alone can lead one to heaven (20:76).

Tazkiyah literally means growth, one example of which can be seen in the tree. A tree is the result of the growth of a seed. When a seed finds a favourable environment, it starts growing until it becomes a green, verdant tree. The same is true of the purification of a human being. In this sense Tazkiyah also covers intellectual development.

God has created a person with great potential, and this potential of the human personality is actualized by Tazkiyah. In this sense it would be right to call it the building of the human personality on a divine foundation.

When a person discovers and realizes faith, he has in actual fact, started the journey of Tazkiyah. Gradually, he becomes a purified soul, or an intellectually and spiritually developed personality. This is the person who will gain entrance into the eternal Paradise of the Hereafter.

There is nothing mysterious about Tazkiyah. Tazkiyah can be attained, not through meditation but through contemplation and reflection. This entails pondering over or thinking about oneself and the universe, and receiving intellectual sustenance for God-realization. This is the process which results in a purified personality. There is nothing abstract about Tazkiyah. It is a known reality. Tazkiyah is the result of a struggle on the part of the individual. It is not at all related to any mysterious inspiration from some supposedly saintly person.

Source: Discovering God