2 Maccabees 12:44
41 So they all blessed the ways of the Lord, the righteous judge, who reveals the things that are hidden; 42 and they turned to supplication, praying that the sin that had been committed might be wholly blotted out. The noble Judas exhorted the people to keep themselves free from sin, for they had seen with their own eyes what had happened as the result of the sin of those who had fallen. 43 He also took up a collection, man by man, to the amount of two thousand drachmas of silver, and sent it to Jerusalem to provide for a sin offering. In doing this he acted very well and honorably, taking account of the resurrection. 44 For if he were not expecting that those who had fallen would rise again, it would have been superfluous and foolish to pray for the dead. 45 But if he was looking to the splendid reward that is laid up for those who fall asleep in godliness, it was a holy and pious thought. Therefore he made atonement for the dead, so that they might be delivered from their sin.
1 Corinthians 15:29
21 For since death came through a man, the resurrection of the dead also came through a man. 22 For just as in Adam all die, so also in Christ all will be made alive. 23 But each in his own order: Christ, the firstfruits; then when Christ comes, those who belong to him. 24 Then comes the end, when he hands over the kingdom to God the Father, when he has brought to an end all rule and all authority and power. 25 For he must reign until he has put all his enemies under his feet. 26 The last enemy to be eliminated is death. 27 For he has put everything in subjection under his feet. But when it says “everything” has been put in subjection, it is clear that this does not include the one who put everything in subjection to him. 28 And when all things are subjected to him, then the Son himself will be subjected to the one who subjected everything to him, so that God may be all in all. 29 Otherwise, what will those do who are baptized for the dead? If the dead are not raised at all, then why are they baptized for them? 30 Why too are we in danger every hour?
Notes and References
"... No early source directly links this final purification of the deceased with the resurrection. Yet, because belief in the resurrection became increasingly wide-spread among Jews in the Second Temple, one may reasonably suppose that acts honoring the dead, including purifying them for burial, were understood to be related to resurrection. That would certainly agree with the Maccabean literature then in circulation that highlighted Jewish hero Judah Maccabee's belief in the resurrection, and his actions to ensure the atonement of dead companions (2 Maccabees 12:43–45) ... Jews of the Second Temple certainly did perform a purification washing for the benefit of their deceased. There is good reason to suppose that many Jews associated the practice with the resurrection, and this conforms well with Paul's remark in 1 Cor. 15:29. Conversely, the Greek denial of resurrection seems to preclude Paul's remark from any association with Greek funerary washings ..."
Ben Keshet, Hanoch 1 Cor. 15:29 and Taharat Hamet: Purification of the Dead as Proof of Resurrection? (pp. 1-19) Kesher, A Journal of Messianic Judaism, 2015