The knowledge pertaining to the interpretation of Arabic letters constitutes an esoteric science of Islam. Over the centuries, it has permeated various domains of Islamic thought, from magical-divinatory practices to philosophical and cosmological reflections, as well as mystical insights within Sufism. The topic has piqued the interest of exegetes, constituting one of the first forms of the interpretation of isolated letters. In Sufi tafsir, the commentary of those letters is characterized by a spiritual dimension that remain largely unexplored. The Laṭāʾif al-Išārāt by Abū l-Qāsim al-Qušayrī, composed in Nishapur in 437 AH, is among the earliest examples of Sufi tafsir. In his commentary on the letters, the author draws upon key interpretations from earlier exegetes, enriching them with allusions to spiritual stations and practices of inner purification. al-Qušayrī's analysis reveals that these letters convey a multiplicity of meanings, but attaining their spiritual understanding requires a path of purification and the unveiling of divine subtleties within the sirr (innermost self) of the disciple.