The Holy Name on His Forehead
It is said that when David, son of Rabbeinu Baruch HaKohen Azog, was born, his father immediately noticed that the holy name Shadai (שדי) was written on the infant's forehead.
He ordered that the child never be let out of the house, or at least that his forehead be covered down to his eyes, so that the holy name would not be exposed to everyone. He explained that anyone who had the misfortune to see the boy's forehead would go blind.