The Messenger of Allah ﷺ said, "The evil eye is real," and he forbade tattooing.
وقال رسول الله ﷺ العين حق ونهى عن الوشم
This is a sahih hadith. Bukhari related it in the Book of Medicine on the authority of Ishaq bin Nasr, and in the Book of Clothing on the authority of Yahya. Muslim related it in the Book of Medicine on the authority of Muhammad bin Rafi. Abu Dawud related it in the Book of Medicine on the authority of Ahmad bin Hanbal.Imam Abu Abdullah Maziri said, the majority of scholars adopted the apparent meaning of this hadith, and said, the evil eye is real. Certain groups of innovators denied it. The proof that their position is unsound is that any concept which is not inherently contradictory, and does not entail the inversion of a reality or the corruption of a proof, falls within the realm of what reason permits. When the divine law reports its occurrence, believing in it becomes obligatory, and denying it is not permissible.Some of the naturalists who affirmed the evil eye held that a poisonous force is emitted from the eye of the one who casts it, which attaches itself to the one affected, causing him to perish or be harmed. This is not accepted, because there is no agent except Allah. The position of the people of the sunnah is that the eye only causes harm and destruction when the one casting it looks, through the act of Allah, the Exalted. Allah has made it the customary course that harm is created when this person confronts another person.As for tattooing, it is pricking the hand with a needle.