The line "you don't believe in the force, do you?" could be repeated to various force users through the trilogy, such as Obi Wan, Yoda, Darth Vader, and the Emperor.

Some examples:

Obi Wan and Luke

"Stay with the droids, they must be delivered safely to Alderaan..."

"You don't believe in the force, do you?"

Yoda and Luke:

"That is why you fail."

"You don't believe in the force, do you?"

Darth Vader and Luke:

"But you're not a Jedi yet...."

"You don't believe in the force, do you?"

The Emperor and Luke:

"Now... you will die."

(as the Emperor smiles) "You don't believe in the force, do you?"