After this Luke narrates that “they” (Silas and Judas) were sent back to Jerusalem (15:33); however, some manuscripts thy to harmonize this verse with v 40, which puts Silas in Antioch, by adding v34: “But it seemed good to Silas to remain.”
Following an irreconcilable disagreement between Paul and Barnabas over John Mark (15:36-39), Paul chose Silas to accompany him through Syria and Cilicia (15:40). Silas had in hand the Jerusalem letter which was also directed to the gentiles in these provinces (15:23). The choice of Silas was certainly astute, since it had the diplomatic advantage of placing the Pauline mission under the auspices of Jerusalem. The presence of Silas could be interpreted by those who knew his Jerusalem stature as a personal legitimation of the Pauline Gosple.
Luke reports that after Timothy joined the mission in Lystra, the group (Paul,Silas,Timothy) went through Phrygia, Galatia, and attempted to go into Bithynia, but, as the result of a vision, they traveled down to Troas instead, then to the port of Neapolis in Macedonia and finally to Phillippi (Acts 16:6-12). There, persuaded by Lydia, the travelers stayed at her home (16:15;40). In Philippi Silas suffered the same fate as Paul: they were oned (16:19-24; 1 Thess 2:2). Freed by an earthquake, the prisoners were taken by the jailer into his house, where he washed their wounds and fed them. Then , according to the narrative, Paul identified both himself and Silas Roman citizens, Romanoi (16:37),after which they were released (16:39). Surprisingly, Paul says nothing about this incident, nor does he mention Silas, in his letter to the Philippians (but see 1 Thess2:2).
Silas is also mentioned in Acts as being with Paul in Thessalonica where both of them (and timothy)