If Gabriel has done something to him to compel him to tell the truth, then Sam has to be incredibly careful about what he says, so instead of answering right off, he takes a deep breath. He can't lie, evidently, but maybe he can talk around the truth. At his sides, his hands clench and unclench.

'Give me one good reason why I should tell you anything.'

He feels the impulse to hotly add that it doesn't matter, it's over, but he's wary of things other than what he intends coming out of his mouth.