Paul chose Timothy to work with him and Silas.

Acts 16:1-3

16 Paul and Silas went to Derbe city and visited the believers there. Next they went to Lystra city. A believer whose name was Timothy lived there. His mother was a Jewish believer, but his father was a Greek. 2 The believers in Lystra and Iconium said good things about Timothy, 3 and Paul wanted to take Timothy with him when he went to other places, so he circumcised Timothy. He did that so that the Jews who lived in those places would accept Timothy, because they knew that his non-Jewish father had not allowed him to be circumcised {anyone to circumcise his son}.