Acts 10:45-46

‘And they of the circumcision who were believers were amazed, as many as came with Peter, because that on the Gentiles also was poured out the gift of the Holy Spirit. For they heard them speak with tongues, and magnify God.'

We do well to pause as we consider this verse. Those who had come with Peter may have been expecting a number of things, and a number of them may have been reluctant to come, but what none of them had expected was that God would give His Holy Unique Spirit to Gentiles. Why, it made them as holy as the Jewish Christians. They had become indwelt by the Lord in the same way, and that even while they were uncircumcised. Note the stress on ‘those of the circumcision.' That was clearly considered important here, and stresses that the others were uncircumcised. The ‘circumcised' consisted of those who had accompanied Peter, and included Peter himself). They were also ‘believers', but they were amazed that God should bless these Gentiles in the same way as He had blessed them,  even though the Gentiles were uncircumcised. They really had no choice but to accept that God was treating them on an equal basis with the Jewish Christians.