In Your Shadow, page 8.

Snape: Heh. 
Still Potter's little tagalong?*

Peter: Let go!

Snape: You're alone, you can't do anything, coward.
Does it feel good to be in Potter's shadow?
If nothing else, keep on living that way.
It suits you.






*[He actually said "goldfish turd", which some people might recognize from Slayers as what Naga is called in reference to Lina.. a goldfish's feces kinda.. trail along after him, y'know? Nasty thing to say, anyway.]