Acts 16:9

And a vision appeared to Paul in the night: There was a man of Macedonia standing, beseeching Paul, and saying, Come over into Macedonia, and help us. And when he had seen the vision, straightway we sought to go forth into Macedonia, concluding that God had called us to preach the gospel unto them.

A vision ... Here is an instance in which God evidently spoke to Paul subjectively, by means of a vision; but the element of uncertainty persists in the fact that they "concluded" that God's message was in the vision, making the decision to rest, in part, upon their deduction, and not as being based on a firm command of the Father.

Regarding the prohibitions which had been placed in Paul's way, forbidding his preaching in Asia and then in Bithynia, and the natural deduction from themselves that they should not return to lands already evangelized, and all this coupled with the instance of Paul's vision; it is not amiss to discover in the providential guidance thus given Paul a substantial amount of deliberate judgment and common sense; nor does this deny the fact that God actually guided them; it is the manner of his doing so which is apparent here.

Straightway we sought to go into Macedonia ... Here surfaces the first of the famous "we" passages of Acts, indicating that at Troas Luke became a member of Paul's company. Boles understood this passage as teaching that Luke was already a preacher of the gospel to the Gentiles, basing it on the following:

Concluding that God had called us to preach the gospel unto them ... By the use of "us," Luke showed that "He included himself with Paul, Silas and Timothy as preachers of the gospel."[3]

Further comment on Luke is made in the introduction to his Gospel in my Commentary on Luke, pp. 3-6.