Harry Potter: Incarcerous!
[Snape blocks the curse]
Harry Potter: Fight back!, you coward! Fight back!
[Bellatrix shoots a curse at Harry]
Severus Snape: No! He belongs to the Dark Lord!
Harry Potter: Sectumsempra!
[Snape blocks the curse again, throwing Harry onto his back]
Severus Snape: You dare use my own spells against me, Potter? Yes. I'm the Half Blood Prince.