Who saw the risen Christ as proof of His resurrection?
As proof of His resurrection, the risen Christ was seen by Cephas (Peter), then by the twelve together, and afterward by more than 500 brethren at one time. Most of those 500 witnesses were still alive when Paul wrote 1 Corinthians, about 31 years later.
Les explains that this is the resurrection chapter, where Paul presents the risen Christ as proof of the resurrection. He was seen first by Cephas, that is Peter, then by the other eleven, or the whole twelve at once. After that, He appeared to over 500 brethren—Jewish believers gathered in the Jerusalem area—at one time. Paul notes that the greater part remained alive when he wrote, about 59 A.D., some 31 years later, so they could still testify that they saw the risen Lord.
And that he was seen of Cephas, then of the twelve: