What is the authenticity of the Hadith: "In the name of Allah, I have veiled myself; and by the power of Allah, I have sought protection. So, whoever intends me ill or plots against me with a scheme is, by Allah's permission, forbidden [from reaching me] and repelled"?

No Hadith with this exact wording has been found, although its meaning is acceptable. It is authentically reported that the Prophet, peace and blessings be upon him, said: "No servant says, every morning and every night, 'In the name of Allah, with Whose Name nothing on earth or in heaven can cause harm, and He is the All-Hearing, the All-Knowing,' three times, except that nothing will harm him." The authentically reported prophetic supplications (adhkar) are sufficient and render others unnecessary.