Al-Risala Al-Qushayriyya (الرسالة القشيرية), written by the Shafi'i-Ash'ari scholar Abu al-Qasim al-Qushayri
Unfortunately, most critical editions use partial tashkil. However, the Dar al-Minhaj edition (Beirut, 2005) has extensive vowel marks. Look for a PDF of that. Al-risala Al-qushayriyya Pdf Arabic