Berakhot 18

One whose close relative died is considered an ‘onen’ and is exempt from commandments. Why? What does it mean “if your dead is before you” – is it to be taken literally? What is forbidden to do in a cemetary if one is close to a dead body so that one does not upset the dead? If the dead can’t see then why will it upset them? There is a question whether or not dead people can see what goes on in this world – and verses and stories are brought to try to come to a conclusion regarding this topic.