There's some evidence that in Galatians 1:4 Paul is citing pre-existing material, more specifically, a theological formula which originated in the Jewish Christian community which explained the theological import of Christ's death. Two main pieces of evidence point in this direction. First, Paul writes "who gave himself" in reference to Christ's death when in most other places he uses the phrasing "was given over." Second, he writes that Christ gave himself "for our sins." This is out of character with Paul's more common use of "sin" in the singular on the one hand and his use of a personal pronoun on the other to describe the beneficiaries of Christ's death. Add to this the parallel with 1 Corinthians 15:3, which Paul states is received tradition, and you have a good case that when Paul writes "who gave himself for our sins" he is using teaching which he received from others.
It's one thing, though, to state that Paul used a theological formula here. It's another to flesh out the import of this analysis. I can think of three important conclusions:
- Assuming that Paul wrote Galatians as one of the earliest of his epistles (I currently hold that Paul wrote Galatians in A.D. 49, on the eve of the Jerusalem Council discussed in Acts 15), this pre-Pauline formula would be evidence that the Christian community from the earliest times saw Christ's death as atoning for sin in some capacity. If Jesus died in A.D. 33, then within 15 or so years after his death, Christians were preaching and teaching the self-directed, sacrificial death of Jesus. It would be difficult to defend a full-orbed substitutionary atonement from this one passage, but it is certainly a constituent, theological part of that doctrine. In other words, that the death of Christ was God's atoning solution for sin was part of the earliest doctrine of the Christian church.
- The presence of pre-Pauline material in his epistles shows that Paul was not a maverick. On the contrary, he was in touch with and in continuity with other Christians, passing along the central teachings he had learned. This strengthens his arguments and shows that it is his opponents who were on the fringe, not him.
- This pre-Pauline formula is critical given the depth of conflict Paul describes in Galatians. This conflict was justified because his opponents were in some aspect turning away from the central teaching about the sacrificial nature of Christ's death. Paul cites this formula here to force his opponents to acknowledge that their disagreement was not over peripheral matters; rather it was a central disagreement over the value of Christ's death, and Paul had early Christian theological reflection on his side.