Augustine of Hippo — as excerpted in the Catena Aurea on Luke 16:27-31

“(de cura pro Mortuis habenda.) But some one may say, If the dead have no care for the living, how did the rich man ask Abraham, that he should send Lazarus to his five brethren? But because he said this, did the rich man therefore know what his brethren were doing, or what was their condition at that time? His care about the living was such that he might yet be altogether ignorant what they were doing, just as we care about the dead, although we know nothing of what they do. But again the question occurs, How did Abraham know that Moses and the prophets are here in their books? whence also had he known that the rich man had lived in luxury, but Lazarus in affliction. Not surely when these things were going on in their lifetime, but at their death he might know through Lazarus’ telling him, that in order that might not be false which the prophet says; Abraham heard us not. (Isa. 63:10.) The dead might also hear something from the angels who are ever present at the things which are done here. They might also know some things which it was necessary for them to have known, not only past, but also future, through the revelation of the Church of God.”