Ed and Lust in “Unfinished Business”

"Wait! Wait a minute! I didn't promise you anything ya know."

"Why?"

"I'm the one who should be asking why. Why do you want to be human? You guys are immortal, aren't you? And you don't even age at all from what I can tell. You can't be hurt and you have powers no human being can ever top. So why should I believe you when you say you wanna give all that up?"

"You don't know how cruel you're being, do you? All right, why do you want your brother to return to the flesh? He's practically immortal too now. It's the same thing, Edward."

"Hold it! The person you were talking about, the one you call 'Master'... Just tell me one thing... Is it somebody that I know?"

"You know something... If you make me human, I just might answer that question."

"Hey! Don't forget... I still have your weakness ya know. [Referring to the locket that contains Lust's human remains.]

"No, Edward... I won't forget about that."