Islam has three dimensions or levels.
They are know as islam, iman, and ihsan.




Islam (submission) refers to having the correct actions, that is, ones that are in accordance with the Quran and Sunna.

Iman (faith) refers to having the correct knowledge (Aqidah).

Ihsan (excellence) refers to having the correct motivations.

Much attention is given to islam and iman and to matters of Shari'a and Aqidah. But Ihsan is important too. Having the correct motivations means purifying our souls from hypocrisy, caprice, heedlessness, and everything else that keeps us from serving Allah SWT for His sake alone.

Tazkiyah and Ihsan can be seen as synonyms of the word Tasawwuf, and refers to the purification of the heart from all the stains that occasionally overcome it. This is due to the abundance of sins and misdemeanours committed by the heart internally and by the organs externally, and the beautifying of the heart through the best qualities and grand exhilaration in the love of Allah which are desired by Shari’a as well. The highest rank of that is ‘al Ihsan’.  Thus, its existence in the time of our beloved Prophet صلي الله عليه و سلم was essential and obvious taking into consideration his rank, status and devotion.

The actual word of Tasawwuf does not exist in the Qur’an within context. However, there are many places in the Qur’an where the synonym of the word has appeared or places where its notion and concept have been discussed.

Following are but a few examples of the mention of Tasawwuf in the Qur’an:

قَدْ أَفْلَحَ مَن زَكَّاهَا

“Indeed he has achieved success who purifies it (the soul)” [Surah as-Shams - 91:9]

هُوَ الَّذِي بَعَثَ فِي الْأُمِّيِّينَ رَسُولًا مِّنْهُمْ يَتْلُو عَلَيْهِمْ آيَاتِهِ وَيُزَكِّيهِمْ وَيُعَلِّمُهُمُ الْكِتَابَ وَالْحِكْمَةَ وَإِن كَانُوا مِن قَبْلُ لَفِي ضَلَالٍ مُّبِينٍ

"It is He who sent among the unlettered ones a Messenger from amongst themselves who recites upon them His Verses, purifies them and teaches them the Book (Qur'an) and Hikmah (wisdom). And verily, before this, they had been in manifest error." [Surah Jumu’ah – 62:2]

جَنَّاتُ عَدْنٍ تَجْرِي مِن تَحْتِهَا الْأَنْهَارُ خَالِدِينَ فِيهَا وَذَلِكَ جَزَاء مَن تَزَكَّى

"Everlasting Gardens, under which rivers flow, wherein they will abide forever: such is the reward of those who purify themselves." [Surah Ta Ha – 20:76]

وَلَا تَزِرُ وَازِرَةٌ وِزْرَ أُخْرَى وَإِن تَدْعُ مُثْقَلَةٌ إِلَى حِمْلِهَا لَا يُحْمَلْ مِنْهُ شَيْءٌ وَلَوْ كَانَ ذَا قُرْبَى إِنَّمَا تُنذِرُ الَّذِينَ يَخْشَوْنَ رَبَّهُم بِالغَيْبِ وَأَقَامُوا الصَّلَاةَ وَمَن تَزَكَّى فَإِنَّمَا يَتَزَكَّى لِنَفْسِهِ وَإِلَى اللَّهِ الْمَصِيرُ

"And a burdened soul cannot bear the burden of another and if one weighed down by burden should call another to carry his it they shall not carry in, even though he is closely related. You warn only those who fear their Lord in secret and keep up prayer; and whoever purifies himself, he purifies himself only for (the good of) his own soul; and to Allah is the eventual coming." [Surah Fatir - 35:18]

قَدْ أَفْلَحَ مَن تَزَكَّى

"Indeed whosoever purifies himself has achieved success." [Surah al-A'laa – 87:14]

فَقُلْ هَل لَّكَ إِلَى أَن تَزَكَّى

"Then say, do you desire to purify yourself?" [Surah Naziaat - 79:18]

الَّذِي يُؤْتِي مَالَهُ يَتَزَكَّى

"He who spends his wealth for increase in self-purification." [Surah Layl - 92:18]

TAZKIYAH & TASAWWUF IN THE HADEETH:

قال: فأخبرني عن الإحسان, قال “أن تعبد الله كأنك تراه, فإن لم تكن تراه فإنه يراك

He (Hadhrat Jibreel عليه السلام) questioned, “What is Ihsaan?” He صلي الله عليه و سلم replied, “That you worship Allah as though you are able to see Him, and if you are not able to see Him then (to bear in mind) that He is watching you." [Saheeh Muslim]

ان الله لا ينظر الى صوركم ولا الى اجسامكم ولكن ينظر الى قلوبكم وأعمالكم

"Indeed Allah does not look towards your appearance and neither towards your bodies (physique) but instead He looks towards your hearts and actions."

ان القلوب لتصدأ كما يصدأ الحديد قيل وما جلاءها يا رسول الله، قال ذكر الموت وتلاوة القرآن

"The Prophet of Allah صلي الله عليه و سلم stated, “Indeed the hearts rust just as metal does.” It was asked, “What is its treatment O Messenger of Allah صلي الله عليه و سلم?” He صلي الله عليه و سلم replied, “The remembrance of death and the recitation of the Qur’an."


I hope that these may help you in your personal jihad against your nafs.

References:

http://simplyislam.blogspot.com/2007/02/tasawwuf-tazkiyya-sufism-reformation.html
http://salaf-us-saalih.com/2010/01/30/tazkiyah-tasawwuf/
http://hamzajennings.com/tasawwuf/