Islam is divided into 3 parts, Islam, Iman and Ihsan. This is how Sufism is rooted in the Sharia. Here is an excerpt of the authentic Hadith of Jibreel.
…My father, Umar ibn al-Khattab, told me: One day we were sitting in the company of Allah’s Apostle (peace be upon him) when there appeared before us a man dressed in pure white clothes, his hair extraordinarily black. There were no signs of travel on him. None amongst us recognized him. At last he sat with the Apostle (peace be upon him) He knelt before him placed his palms on his thighs and said: Muhammad, inform me about al-Islam. The Messenger of Allah (peace be upon him) said: Al-Islam implies that you testify that there is no god but Allah and that Muhammad is the messenger of Allah, and you establish prayer, pay Zakat, observe the fast of Ramadan, and perform pilgrimage to the (House) if you are solvent enough (to bear the expense of) the journey. He (the inquirer) said: You have told the truth. He (Umar ibn al-Khattab) said: It amazed us that he would put the question and then he would himself verify the truth. He (the inquirer) said: Inform me about Iman (faith). He (the Holy Prophet) replied: That you affirm your faith in Allah, in His angels, in His Books, in His Apostles, in the Day of Judgment, and you affirm your faith in the Divine Decree about good and evil. He (the inquirer) said: You have told the truth. He (the inquirer) again said: Inform me about al-Ihsan (performance of good deeds). He (the Holy Prophet) said: That you worship Allah as if you are seeing Him, for though you don’t see Him, He, verily, sees you.. .. He (the narrator, Umar ibn al-Khattab) said: Then he (the inquirer) went on his way but I stayed with him (the Holy Prophet) for a long while. He then, said to me: Umar, do you know who this inquirer was? I replied: Allah and His Apostle knows best. He (the Holy Prophet) remarked: He was Gabriel (the angel). He came to you in order to instruct you in matters of religion.“
So, in Islam, every part of the deen has a science. Fiqh is the science of Islam, which governs the limbs. This is our ritual prayer, the ritual ablution, how to fast, etc… Aqeeda (Creed) is the science of iman (faith), which teaches us proper belief and how we have to belief in angels and the messengers peace be upon them etc. Iman corresponds to the heart and mind. Finally there is ihsan, which is focused on the heart, the consciousness and inward behavior. It’s corresponding science is tasawwuf or Sufism.
“Islam is the outward which is made erect by Iman the inward, and it is perfected by Ihsan; a palpable consciousness of God comparable to “seeing.”
Quran, 22:46 …Truly it is not their eyes that are blind, but their hearts which are in their breasts.
More on the heart:
Presence of heart is what substantiates outward worship.
“Verily, God does not look to your bodies nor to your forms but He looks to your hearts.” [Muslim]
“… if it is sound, the entire body is sound and if it is corrupt
the whole body is corrupt.” [Bukhari]
So this is all what tasawwuf is about. It is about purifying the heart from what makes hearts go blind. Sufism can be called the science of ihsan. It is just as much of a science of Sharia as is fiqh and aqeeda. So people that reject it are rejecting a whole third of Islam.
Its beginning is knowledge, its middle is action and its end is bestowed.” [Sidi Ahmad ibn `Ajiba al-Maliki]
“To avoid any misinterpretation of what is implied by the words Sufi and “Sufism” in Arabic: tasawwuf, the fact of wearing a garment made of wool-suf-as an emblem of purity) was adopted to designate the quest fro spiritual illumination, while sufi was applied to characterize the person who had attained an obvious degree of proximity to God. This indicates that Sufism has always been embedded in the texture of the Islamic creed, representing an ideal mode of worship derived from the Quranic Revelation and from the customs and sayings (sunna and hadith) of the Prophet Muhammad, and then transmitted without interruption throughout the centuries.”
What about the different Sufi orders?
“They basically represent different methods, without there being any possibility of a fundamental difference of doctrine, for the doctrine of Unity is unique” (at-tawhidu wahid)
Was this around at the time of the Prophet? (May Allah bless him and give him peace)
“For those who say, “Where did the name tasawwuf come from? It was not received from the Prophet (May Allah bless him and give him peace)…the Prophet (May Allah bless him and give him peace) never said Sufiya? Did the Prophet (May Allah bless him and give him peace) mention Muhaddithun(Peopleof Hadith)? Did the Prophet (May Allah bless him and give him peace) tak of Huffadh (memorizers of Quran)? Did the Prophet (May Allah bless him and give him peace) talk about the Usuliyun (People of the principle of religion)? Did the Prophet (May Allah bless him and give him peace) talk of the Shaykh of Islam? Did the Prophet (May Allah bless him and give him peace) talk of the Mufti? The Prophet (May Allah bless him and give him peace) did not use these words, but this community has constructed technical terms…” (Habib Ali al Jifri)
If anyone has any suggestions or corrections or additions, feel free!