They that were of the circumcision (hoi ek peritomēs). Literally, those of circumcision (on the side of circumcision, of the circumcision party). The phrase in Act 10:46 is confined to the six brethren with Peter in Caesarea (Act 11:12). That can hardly be the meaning here for it would mean that they were the ones who brought the charge against Peter though Hort takes this view. All the disciples in Jerusalem were Jews so that it can hardly mean the whole body. In Gal 2:12 the phrase has the narrower sense of the Judaizing or Pharisaic wing of the disciples (Act 15:5) who made circumcision necessary for all Gentile converts. Probably here by anticipation Luke so describes the beginning of that great controversy. The objectors probably did not know of Peter’s vision at Joppa, but only of the revolutionary conduct of Peter in Caesarea. These extremists who spoke probably had abundant sympathy in their protest. The apostles are mentioned in Act 11:1, but are not referred to in Act 11:2. Apparently they are in contrast with the circumcision party in the church.
Contended (diekrinonto). Imperfect middle of the common verb diakrinō, to separate. Here to separate oneself apart (dia), to take sides against, to make a cleavage (dia, two, in two) as in Jud 1:9. So Peter is at once put on the defensive as the contention went on. It is plain that Peter was not regarded as any kind of pope or overlord.