Tasawwuf is A Basic Principle of Deen
"Deen (faith) is something that does not accommodate alteration and modification. It is the Tauheed and the Ikhlas that all of the Prophets (AS) brought." [Tafseer-e-Jumal 497:1]
Benefit: This proves that Islamic Tasawwuf (Ikhlas) is a basic principle of the Deen, which is filled with Ikhlas and Ihsan. Without Ikhlas, neither Tauheed nor faith and actions are acceptable (to Allah).
Meanings of Terms
Ikhlas/Ihsan: Sincerity; devotion. To worship and remember Allah as if one sees Him, or is present before Him. (See Hadeeth-e-Ihsan)
Tauheed: The Oneness of Allah.