We should remember (mnēmoneuōmen). Present active subjunctive, “that we should keep on remembering.”
Which very thing (hȯ̇auto touto). Repetition of relative and demonstrative, tautology, “which this very thing.” In fact Barnabas and Saul had done it before (Act 11:30). It was complete victory for Paul and Barnabas. Paul passes by the second public meeting and the letters to Antioch (Acts 15:6-29) and passes on to Peter’s conduct in Antioch.