Meanwhile, it may be asked, what happened to the Gentile Christians who accompanied Paul to Jerusalem [ACTS 21:17]? Two of them seemed to have stayed on in Judaea, Luke and Aristarchus; perhaps they went to Caesarea so as to be near Paul and perform what services they could for him. The others probably made their way home as quickly and unobtrusively as they could: the turn of events which they had witnessed in Jerusalem may well have frustrated the realization of Paul's hopes that his Gentile churches would find that the collection forged a bond of affection between them and their Judaean brethren. Whether the Judaean brethren in their turn felt more closely drawn to their Gentile fellow-Christians "because of the surpassing grace of God" manifested in their generous gift (2 CORINTHIANS 9:14) we have no means of knowing.
Neither have we any means of knowing if the Jerusalem church or its leaders exerted themselves at all on Paul's behalf when they saw the predicament into which their well-meant counsel had brought him. Probably they felt relieved when they heard that he had been taken to Caesarea. This last visit of Paul's to Jerusalem had followed the pattern of earlier visits: trouble had broken out once more. It would really be best if Paul never came to Jerusalem again. Now that he was in Caesarea, under Roman guard, he was probably out of immediate danger, but in any case there was little that they could do for him. Moreover, the high priest and Sanhedrin were engaged in prosecuting him, and it would be unwise to do anything which might unnecessarily attract their hostile attention. It is easy to credit the Jerusalem church and its leaders with unworthy motives, but some attempt should be made to appreciate the extreme difficult situation in which they found themselves. If they still took serious their commission to evangelize their fellow-Jews (and there is no reason to suppose that they had ceased to do so), any public association with Paul would have been a major handicap to its prosecution. It is possible, indeed, that this association was one of the grounds for the illegal execution of James the Just at the instance of the high priest Ananus II during the interregnum in the procuratorship which followed the death of Festus (A. D. 62).
from pages 358-359, Paul: Apostle of the Heart Set Free