Commentary for Berakhot 6:18

To be an auditor of a discussion on Torah and not take part in it was a mark of ignorance and one incurred shame thereby. The dead, being unable to participate, although for other reasons, would thus be disgraced. The idea will not seem so fantastic in view of the belief that the corpse was conscious of what transpired in its presence. Cf. the discussion on pp. 120 ff.