What is the "blockade" (al-hisaar) practiced by some Sufis as a form of ruqyah for protection against black magic, and does it have any basis in the Prophet's Sunnah?

The Sunnah does not mention what is called "the siege" or "fortification against black magic," and it is forbidden to attribute any Hadith to the Prophet, peace be upon him, without verifying its authenticity.

Allah has legislated means of fortification against magic and evils, including: 1. Maintaining obedience to Allah: by performing the obligatory acts, avoiding prohibitions, repenting, drawing closer to Allah through supererogatory acts, and relying on Allah. 2. Maintaining the morning and evening remembrances: Reciting Ayatul Kursi and the last two verses of Surat Al-Baqarah. Reciting Surahs Al-Ikhlas, Al-Falaq, and An-Nas three times. Saying: "In the Name of Allah, with Whose Name nothing on earth or in the heaven can cause harm, and He is the All-Hearing, the All-Knowing" three times. Saying: "I seek refuge in the perfect words of Allah from the evil of what He has created" three times. 3. Eating seven Ajwa dates in the morning: Whoever does this will not be harmed by poison or magic on that day.

It is obligatory to adhere to the Book (Quran) and the authentic Sunnah, and to beware of innovations.