John Calvin Commentary Acts 16:1

"And he came also to Derbe and to Lystra: and behold, a certain disciple was there, named Timothy, the son of a Jewess that believed; but his father was a Greek." — Acts 16:1 (ASV)

Luke now begins to declare what Paul's proceedings were after Barnabas and he had separated. First, he shows that at Lystra he took Timothy into his company to be his companion. But, so that we may know that Paul did nothing rashly or without good consideration, Luke says plainly that Timothy was a man whom the brethren highly approved of, and that they testified to his godliness; for Luke states it quite literally.

And so Paul himself observes a similar principle in choosing, which he elsewhere commands to be followed in choosing ministers (1 Timothy 3:7). Nor should it be thought that those prophecies with which Timothy was set forth and adorned by the Spirit had even then come to light, as Paul testifies elsewhere (1 Timothy 1:18). But there seems to be some disagreement in this: Luke says that Timothy was well reported of among the brethren, while Paul requires that one chosen to be a bishop should have a good report from those who are outside.

I answer that we must principally look to the judgment of the godly, as they are the only fit witnesses and alone discern rightly and wisely according to the Spirit of God; and that we ought to attribute no more to the wicked than to blind men. Therefore, it appears that godliness and holiness of life must be judged according to the will and consensus of godly men, so that he whom they commend may be considered worthy to be a bishop.

Nevertheless, I confess that this also is required in the second place: that even unbelievers should be constrained to commend him, lest the Church of God be endangered by their slanders and evil speaking, if it allows itself to be governed by men of bad reputation.