Prof Snape: You’ve kept him alive so that he can die at the proper moment. You’ve been raising him like a pig for slaughter!
Prof Dumbledore: Don’t tell me now that you’ve grown to care for the boy.
[Snape casts a Patronus in the shape of a doe, just like Lily’s - the same one that helped Harry find the Sword of Gryffindor]
Prof Dumbledore: Lily… After all this time?
Prof Snape: Always.