Indeed, no lover seeks union without his beloved seeking him. But the love of lovers makes their bodies into bowstrings, while the love of beloveds makes them happy and plump. When the lightning of love for the loved one flashes in *this* heart, know that there is also love in *that* heart. When love for God has doubled in your heart, without doubt God has love for you. You have never heard one hand clapping without the other. The thirsty man laments, "Oh sweet water!" The water also laments, "Where is the drinker!" This thirst in our souls is the attraction of the Water - we belong to It and It belongs to us. Jalaluddin Rumi's Mathnawi, book 3, vv. 4393-4399, from "The Sufi Path of Love," translated by W. C. Chittick, p.209.
Sufism is defined by its adherents as the inner, mystical dimension of Islam. A practitioner of this tradition is generally known as a ṣūfī Sufis believe they are practicing ihsan (perfection of worship) as revealed by Gabriel to Muhammad: "Worship and serve Allah as you are seeing Him and while you see Him not yet truly He sees you".. Sufism is opposed by Wahhabi and Salafist Muslims.(adapted from Wikipedia)