Shams al-Din al-Daylami's classic work, 'Muhimmat al-Wasilin', is a foundational text in Islamic mysticism. It serves as a detailed guide for Sufi practitioners who have reached advanced stages of spiritual realization, known as the 'Wasilin' or 'the Arrived'. The book meticulously outlines the essential duties, spiritual disciplines, ethical conduct, and internal states required to maintain and deepen their connection with the Divine. Al-Daylami explores concepts like constant remembrance (dhikr), contemplation, and the virtues of the spiritually mature, making it an indispensable resource for understanding the practical and theoretical aspects of the advanced Sufi path.