Jamieson, Fausset and Brown on Acts 15:12

12. Then all ... gave audience to Barnabas and Paul--On this order of the names here, see on Ac 15:25.

declaring what miracles and signs God wrought among the Gentiles by them--This detail of facts, immediately following up those which Peter had recalled to mind, would lead all who waited only for divine teaching to see that God had Himself pronounced the Gentile converts to be disciples in as full standing as the Jews, without circumcision; and the attesting miracles to which Paul here refers would tend, in such an assembly to silence opposition.