2 Maccabees 12:43-46

And, calling an assembly, he sent twelve thousand drachmas of silver to Jerusalem, to be offered for a sacrifice for the sins of the dead, thinking well and religiously about the resurrection, (for if he had not hoped that those who had fallen would be resurrected, it would have seemed superfluous and vain to pray for the dead,) and because he considered that those who had fallen asleep with piety had great grace stored up for them. Therefore, it is a holy and beneficial thought to pray on behalf of those who have passed away, so that they may be released from sins.