The great Imam of Tasawwuf and founder of the Shadhili tariqa Sidi Abul Hasan as-Shadhili (ra) said:
The most direct path to God is founded upon four things. He who accomplishes them [all] is one of the true mystics, well-versed in the secrets of reality (siddiqin muhaqqiqin). He who accomplishes three of them is one of the friends of God (wali) who have been drawn near to Him. He who accomplishes two of them is one of the firmly believing martyrs (shuhada’). He who accomplishes one of them is one of the upright servants of God. The first of these four is remembrance (dhikr), the degree (bisat) of which is righteous works, and the fruit of which is illumination. The second is meditation (tafakkur), the degree of which is perseverance, and the fruit of which is knowledge (‘ilm). The third is spiritual poverty (faqr) the degree of which is thankfulness, and the fruit of which is an increase in it. The fourth is love (mahabba), the degree of which is disdain for the world and those of it, and the fruit of which is union with the beloved.