What are the verses and supplications for protection (tahsin)? When should the protection be performed? And should this protection be performed before or after treatment?

It is prescribed to protect oneself with the Quran and remembrances (adhkar) before and after treatment. Among the verses and surahs for protection are: Surat Al-Baqarah, Al-Ikhlas, Al-Mu'awwidhatayn (Al-Falaq and An-Nas), Ayatul-Kursi, and the last verses of Surat Al-Baqarah.

Among the narrations mentioned in this regard: reciting Surat Al-Ikhlas and Al-Mu'awwidhatayn three times in the morning and evening is sufficient against everything; saying "Hasbi Allahu la ilaha illa Huwa, alayhi tawakkaltu, wa Huwa Rabbul-Arshil-Azeem" (Allah is sufficient for me; there is no deity except Him. Upon Him I have relied, and He is the Lord of the Great Throne) seven times in the morning and evening is sufficient against the worries of this world and the Hereafter; that Satan flees from a house in which Surat Al-Baqarah is recited; that reciting Ayatul-Kursi before sleeping protects one from Satan; that reciting the last two verses of Surat Al-Baqarah at night is sufficient; and that Satan does not approach a house in which these two verses are recited for three nights.

For remembrances in general, it is advisable to refer to Al-Qahtani's book "Hisnul Muslim" (Fortress of the Muslim) and his book "Adh-Dhikr wad-Du'a wal-Ilaj bir-Ruqa min al-Kitab was-Sunnah" (Remembrance, Supplication, and Treatment with Ruqyah from the Book and Sunnah), as they provide detailed information about protection.