My sister is possessed by a devil. She falls unconscious and weeps a lot.
I hope you will give me a Du`a' (supplication) to use for treating her.
The possessed and the epileptic may be treated by the Qur'an, especially, Surah Al-Fatihah, Ayat-ul-Kursy (Surah Al-Baqarah, 2:255), Surah Al-Ikhlas (Surah no. 112), Al-Mu`awwidhatayn (Surahs Al-Falaq no. 113 and Al-Nas no. 114) and the permissible supplications. You may refer to the book of "Al-Adhkar" by (Part No. 1; Page No. 104) Imam Al-Nawawy, "Al-Kalim Al-Tayyib by Shaykh-ul-Islam
Ibn Taymiyyah and Al-Wabil Al-Sayyib by
Ibn Al-Qayyim (may Allah be merciful to them).May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.