From the episode "The Pirate Solution"

Sheldon: "I got some extra money from the head of the department, and Raj can come work for me."

Raj: "You want me to work with you?"

Sheldon: "For me. You're going to have to listen more carefully when you're on the job."

Raj: "Please don't take this the wrong way, but I'd rather swim buck-naked across the ganges with a paper cut on my nipple and die a slow, agonizing death from a viral infection than work with you."

Sheldon: "For me."

(this footage belongs to CBS, not me)