Originally Posted by
The book
“Without meaning to, as you now know, Lord Voldemort doubled the bond between you when he returned to a human form. A part of his soul was still attached to yours, and, thinking to strengthen himself, he took a part of your mother’s sacrafice into himself. If he could only have understood the precise and terrible power of that sacrifice, he would not, perhaps, have dared to touch your blood. . . . But then, if he had been able to understand, he could not be Lord Voldemort, and might never have murdered at all.
“Having ensured this two-fold connection, having wrapped your destinies together more securely than ever two wizards were joined in history, Voldemort proceeded to attack you with a wand that shared a core with yours. And now something very strange happened, as we know. The cores reacted in a way that Lord Voldemort, who never knew that your wand was a twin of his, had ever expected.
“He was more afraid than you were that night, Harry. You had accepted, even embraced, the possibility of death, something Lord Voldemort has never been able to do. Your courage won, your wand overpowered his. And in doing so, something happened between those wands, something that echoed the relationship between their masters.
“I believe that your wand imbibed some of the power and qualities of Voldemort’s wand that night, which is to say that it contained a little of Voldemort himself. So your wand recognized him when he pursued you, recognized a man who was both kin and mortal enemy, and it regurgitated some of his own magic against him, magic much more powerful than anything Lucius’s wand had ever performed. Your wand now contained the power of your enormous courage and of Voldemort’s own deadly skill: What chance did that poor stick of Lucius Malfoy’s stand?”