Did the centurion call Jesus the Son of God or a righteous man?

There is no reason to think the centurion said only one sentence. He watched Jesus die after three hours of darkness, followed by the earthquake (Matthew 27:45–54), and Matthew says that he and “they that were with him” spoke out in fear, so more than one soldier may have said more than one thing. Each Gospel records the words that suit its account.

Luke’s Gospel stresses again and again that Jesus was innocent: Pilate says three times that he finds no fault in him (Luke 23:4, 14, 22), Herod found nothing worthy of death (23:15), and the penitent thief says “this man hath done nothing amiss” (23:41). The centurion’s ‘righteous’ (dikaios) can mean ‘innocent’, and Luke makes his verdict the climax of that theme. Matthew and Mark give his confession that Jesus was ‘the Son of God’. The two belong together: Jesus had been condemned for claiming to be the Son of God (Matthew 27:43; John 19:7), so if he was righteous, his claim was true. A Roman soldier may have meant less by ‘son of God’ than a Christian reader would, but all three Gospels show the officer in charge of the execution concluding that Jesus was not what his accusers said. Gill puts both sayings together in just this way.