“Be my witness” - so says Jesus to Paul.

Witness of what? Paul never met Jesus in the flesh, didn’t see the crucifixion, didn’t go to the empty tomb. Jesus came to Him in a flash of light and a voice. Is that it?

Kavin Rowe ( World Upside Down: Reading Acts in the Graeco-Roman Age ) hints at an alternative explanation by calling attention to how Stephen’s martyrdom, “witnessed” by Paul, works in the book of Acts: “Whether or not Luke was here consciously forging the first explicitly verbal link between ‘witnessing’ and becoming a ‘martyr’ in the later Christian sense of the term, the text doubtless draws clearly the line between the mission of witnessing to the risen Jesus and the reality of trial, suffering, and death. In so doing, it elevates for clear inspection what it means to be a witness in the missionary theology of Acts. It is, in fact, to reenact the life-pattern of the suffering Christ, to suffer for his Name, to be put on trial, to face the possibility of death, and to proclaim the resurrection. In short, it is to embody the cruciform pattern that culminates in resurrection.”

Paul was not a witness to the death of Jesus, but to the death of the “witness” of Jesus. To put it differently, what Paul has witnessed is not the death of Jesus but the death of Jesus in the suffering of His disciples.