John Gill Commentary Acts 23:17

"And Paul called unto him one of the centurions, and said, Bring this young man unto the chief captain; for he hath something to tell him." — Acts 23:17 (ASV)

Then Paul called one of the centurions unto him
For under this chief captain there must have been ten of them, if the company of which he was captain consisted of a thousand men, as his title chief captain or chiliarch imports; for a centurion was over an hundred men, as his title signifies; perhaps this might be the same, as in (Acts 22:25Acts 22:26)

and said, bring this young man to the chief captain :
which was a very prudential step, not to let the centurion into the secret, but to desire him to introduce the young man to the chief captain; for had he trusted the centurion with it, he might not have acquainted his officer with it, but have informed the liers in wait of it.

Now though the apostle was assured by Christ that he should not die at Jerusalem, but should bear witness of him at Rome, and though he did not distrust the truth of Christ's words, but most firmly believed them, yet he thought it his duty to make use of the means, which providence had put in his way, for his preservation and safety. The Ethiopic version reads, "bring this young man by night to the chief captain"; that so he might not be seen, and observed to have carried any intelligence to him.

for he has a certain thing to tell him ;
which was of some moment and importance, and proper for him to know.