Wikipedia
Tazkiah (تزكية) is an Arabic-Islamic term alluding to "tazkiyah al-nafs" meaning "purification of the self". This refers to the process of transforming the nafs (carnal self or desires) from its deplorable state of ego-centrality through various spiritual stages towards the level of purity and submission to the will of Allah. Its basis is in learning the shari'ah and deeds from the known authentic sunnah ('ilm) and applying it in your own deeds through life resulting in spiritual awareness of Allah (being constantly aware that He is with us by His knowledge and knows all that we do, along with being in constant remembrance or Dhikr of Him in your thoughts and actions) being the highest level of Ihsan.
Tazkiah (and the related concepts of tarbiyah and talim – training and education) does not limit itself to the conscious learning process: it is rather the task of giving form to the act of righteous living itself: treating every moment of life with remembering one's position in front of Allah.