1 Corinthians 15:29 (ESV)

29 Otherwise, what do people mean by being baptized on behalf of the dead? If the dead are not raised at all, why are people baptized on their behalf?

Up to this point in the discourse, Paul has highlighted the close connection between the resurrection of Christ and the future resurrection of Christ’s people. Now (from 1 Corinthians 15:29–34) he will highlight the connection between belief in the future resurrection and the way in which we live our lives in the present age. As in other places in the letter (e.g., 1 Corinthians 12:29–30), Paul asks a series of rhetorical questions that should prompt the Corinthians to think and reflect.

Does being baptized on behalf of the dead refer to a substitutionary baptism, in which believers had themselves baptized on behalf of unbaptized loved ones who had died? The Greek preposition huper (over, for, or on behalf of) allows for this interpretation. Yet there is no evidence of such a practice in the early church (although, in later centuries, some sects developed a practice of substitutionary baptism and found a basis for it in this verse).

If such a practice did indeed exist in Paul’s time, he would surely have viewed it as incompatible with the gospel. This could be the reason why he refers to these people in the third person. Rather than associating himself with them in their superstition, he uses them as an example to prove his point. Without the hope of a resurrection, they would not have any motive for doing what they did.

Some early church fathers have interpreted Paul’s words in a different manner. They held that he was referring to the dead bodies of these baptized believers themselves. His question could then be rephrased as follows: Otherwise, what do people mean by being baptized for the sake of their own corpses? Understood in this way, Paul would be referring to Corinthian church members who were baptized despite having no hope of a resurrection.

Against this interpretation it should be noted that Paul does not seem to be speaking about the Corinthians at all. He does not use the words you and your (see, by contrast, 1 Corinthians 15:12, 1 Corinthians 15:14), but instead speaks only of people. This suggests that he is thinking of people outside the Corinthian church.

Another possibility is that Paul is referring not to Christian baptism but to Jewish ceremonial washing. The same Greek word is used for both rituals (e.g., in Mark 7:4 and Hebrews 9:10 the words baptizo and baptismos refer to ceremonial washing). If Paul is actually referring to washing, then the people of whom he speaks are not Christians but Jews.

The Corinthian church was originally a splinter group of the Jewish synagogue. They would have been well aware of the Mosaic law that stipulated that a person who had touched a dead body had to purify himself by washing (Numbers 19:1–22). If we interpret Paul’s question in light of this law, it could be rephrased as follows: Otherwise, what do people (that is, the Jews) mean when they wash themselves for the sake of dead bodies? In other words: If the death of the body is not something which we need to be saved from, why did God declare a dead body unclean, and something of which we need to purify ourselves?

Having looked at only three possible interpretations (there are many more), we should acknowledge that we as modern readers still lack the background information that is needed to fully understand this verse. All we can say for sure is that the practice referred to in this verse is one for which there would not be any motive, had God not promised to raise the dead.